[From the U.S. Government Printing Office, www.gpo.gov]


                                                               FY V1            Task 14

                                                                   Final Product
                                                                 VA Coasta(g(esources Mgt. Tmgrwn

                                                                       12AIA)2


                 Dra- inie                    d'.               air
                 Rc@source Ma"IM
                      For Systems Failing in@ the
                    Coastal Zone Area Of Vi.r
                                           I Rep








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                                 Produced bythe VVirginia Department of Health
                                   Division of Onsite Sewaze and Water Ser-viceS
                                          Througha. Grant Funded"'by NOAA and
                                Administered by-- the Council on the Environm.eht







                     tructc             n  S@,
               Cons          kd. Wetla d.
               for Wastewater Treatment
               Municipal, Industrial and Agricultural


               Donald A. Hammer
               Editor


















                                                          71


                              ZZ...
         RF








                                           S Li







          0M.                        Class outline
                             Drainfield Repair Technology
                         October 26-27, 1992 (Virginia Beach)
                             October 27-28 (Newport News)
        [BEL                            Class 1

         October 26, 1992
         Virginia Beach Central Library

         9:00 - Noon           High Pressure Drip Irrigation
                               Design and Application
                               Instructor: Tom Sinclair


         Noon - 1:30           Lunch
                                                          U . S . DEPARTMENT OF COMMERCt. -NOAA
         1:30 - 4:30           Recirculating Sand FiltersC OASIAL SERVICES CENTER
                               Design and Application
                               Instructor:  Rich Piluk    2234 SOUTH HOB&ON AVENUE-
                                                          CHARLESTON, SC 29405'241@.'-
         October 27, 1992
         Virginia Beach Health Department

         9:00 - 11:15          Constructed    Wetlands   and    Upland-Wetland
                               systems.
                               Application, design and use in North Carolina'..
                               Halford House
  - 0
         11:15 - Noon          Constructed Wetlands, Virginia's Experimental
                               Program Experience

                                        Class 2
                                                      r
         October 27, 1992                             Propo::ty Clf @7'C L-4brary
         Newport News Health Department

         1:30 - 4:30 p.m.      High Pressure Drip Irrigation
                               Design and Application
                               Instructor: Tom Sinclair


         October 28, 1992
         Newport News Health   Department

         9:00 - Noon           Recirculating Sand Filters
                               Design and Application
                               Instructor: Rich Piluk

         1:30 - 3:45 p.m.      Constructed    Wetlands   and    Upland-Wetland
                               systems.
                               Application, design and use in North Carolina
                               Halford House
  J-0 3:45 - 4:30 p.m.         Constructed Wetlands, Virginia's Experimental
                               Program Experience











                                     Class Outline
                       Theory of Drainfield Failure and Repair

                           October 19, 1992 (Virginia Beach)
                            October 20r 1992 (Newport News)
                           October 21, 1992 (Glenns Campus)

          9:30 - 9:45 a.m.     Introduction & Welcome

          9:45 - 10:45 a.m.    overview of why systems fail
                               Instructor: Alexander


          10:45 - 11:00 a.m.   Break


          11:00 - Noon         Systematic approach to evaluating the cause(s)
                               of a failing system.
                               Instructor: Jones


          Noon - 1:00 p.m.     Lunch

          1:00 - 2:30 p.m.     Repair strategies to correct failing systems
                               Instructor: Sandman


          2:30 - 2:45 p.m.     Break

          2:45 - 4:00 p.m.     Repair options and matching technology to
                               solutions.   The most expensive repair isn't
                               necessarily the best.
                               Instructors: Alexander and Sandman

          4:00 - 4:30 p.m.     Wrap-up.    Questions, answers and general
                               discussion.






    This training class was funded, in part, by the
    Virginia Council on the Environment's Coastal
    Resources Management Program through Grant
    #NA170ZO359-01 of the National Oceanic and
    Atmospheric Administration, Office of Ocean and
    Coastal Resource Management, under the Coastal
    Zone Management Act of 1972 as amended





         Repair Training Expectations

      ï¿½ Improve understanding about why systems fail


      ï¿½ Improve ability to I.D. causes


      ï¿½ Provide basis for designing an appropriate
        repair


      ï¿½ Generate internal interest


      ï¿½ Instill public confidence
          * what helps?
          * what hurts?
      0                     0                      0


				Class Perspective


			Informal (ask questions)


			Encourage creativity


			Encourage long term innovative thinking


			Variation between Specialists


			Variation in time






                    Introduction

		Treatment


		Biological Components
			Bacteria
			Viruses


		Physical and Chemical Components

			BOD
			SS
			Nitrates
			Other


		Disposal



		
           	
		



	





                 Causes of Failure
                 Hydraulic Failure


			Loading rates


			Miscellaneous water sources


			Leaking fixtures


			Uneven distribution


			




                 Causes of Failure
               * Physical Causes *


                 0 Tree roots


               1 0 Age

                 9 Material failure
                     * construction damage
                     * settling

                 9 Soil clogging
                     * creeping failure
                     * mineralogy changes
      ID                     0                      0






                  Causes of Failure
              * Landscape Position

				Infiltration


				Off-site drainage
                     






                 Causes of Failure
                  * Problem Soils *


                   High water tables


                   Slow infiltration rates


                   Plastic clays


                   Restrictive horizons





      




            A Systematic Evaluation
           The House and Plumbing


             ï¿½ Introduction
                 logical approach
                 keys solution to problem
                 requires thought on each site
                    (no cookbook solutions)

             ï¿½ Leaking fixtures

             ï¿½ Obstructed vent


             ï¿½ Obstructed sewer


SCUM

                   LIQUID                                     TO 
                                                           ABSORPTION 
                                                            FIELD

                                 SLUDGE                    




















                                                  

























                                                                                                                Scum
                                                                                                                    
                                                                                                                



                                                                                                               Liquid                     To Absorption Field
                                                                            



                                                                                                              Sludge
 




               A Systematic Evaluation
                     The Septic Tank


                   Maintenance
                     When pumped
                     Observations when pumped
                   Records and history
                     This system
                     Neighboring systems

                  ï¿½ Tees
                     Present?
                     Condition
                     Materials

                  ï¿½ Effluent level





            A Systematic Evaluation
                * Distribution Box *


                  0 Condition and materials
                      Tree roots
                      Timing
                      Presence of sludge


                  9 Effluent level


                  * Relative elevation to
                      Septic tank outlet
                      Drainf ield
      0                      0                      0





            A Systematic Evaluation
                 * The Drainf ield


               * System age and size
               9 Surface drainage

               9 Lines saturated?

               * Evidence of physical damage
               *Clogging mat present?
                 Depth to limiting factor
                   water table
                   impervious horizon
                   plastic soils
















                 TRADITIONAL SUBSURFACE SEEPAGE BED:
                                                        Gravity flow; continuous trickle of effluent.


                                      - - - - - - - - - - - - - - - - - - -



                                4W



                                                 -- - - - - - - - - - - - - - -








                                             - - - - - - - - - - - - - - - - -


                                                     4W




                                              -----------------


                                   4   4   1       4       4

                                                                                      Equilibrium


                                                   4 4 1 4 4 1



                 Figure 17. Progressive clogging of the infiltrative surfaces
                                 of subsurface absorption systems (11)





                  Repair Strategies
                 * Loading Rates *

           ï¿½ Hydraulic loading rates (LTARS)

           ï¿½ Unaccounted for sources

           ï¿½ Dosing

           ï¿½ Distribution

           ï¿½ Water use reduction
               passive devices
               active measures (behavior changes)
           ï¿½ Water use management

           ï¿½ Surface water diversion
                                                    0






                Repair Strategies
              * Physical Causes *

                Replace damaged component


                Tree roots


                Improper venting







     
 




                 Repair Strategies
             * Landsca e Position *


             9 Relocate drainfield


             e French drain
                 limited solution
                 critical design


             e Management of surface run-off


             9 Water use reduction


      0                                             0





                  Repair Strategies
           * Soil Related Problems *


                   9 Water table
                       shallow installation
                       pretreatment


                   9 Slow rates
                       shallow installation
                       increase size
                       -improve distribution



      0                       0                       0





                      Repair Strategies
                   Soil Related Problems


              ï¿½ Soil clogging
                  evaluate longevity of previous system
                  replace drainfield
                  evaluate size and condition of tank

              ï¿½ Plastic clays
                  water use management

              ï¿½ Restrictive horizons
                  shallow or deep installations
                  f rench drain
                  modify size
                  improve distribution
                  modify trench spacing





                   Component Functions
                         Pretreatment


                   Septic Tank vs Dual Septic Tank
                     tees
                     Zabel f ilter

                 9 Sand Filters
                     trickling
                     intermittent
                     recirculating

                 o Aerobic Pretreatment
                     Class I
                     Class 11

                 * Constructed Wetlands





              Component Functions
        Final Treatment and              isposal


               9 Drainfield
                   distribution boxes
                   flow diversion valves


               e Enhanced- flow


               * Low pressure distribution


               9 Elevated sand mounds


               9 High pressure drip disposal





               Component Functions
           * Blackwater Treatment *


                     9 Composting toilets


                     9 Vault privies


                     9 Incinerating toilets

                                     a







      0                                                10






   0






                            The Systematic Evaluation
                                      . and Repair of
                                 Failing Drainfields in
                              the Coastal Zone Area of
                                            Virginia


  0




















             By: Donald J. Alexander, M.S.
                   Calvin Jones
                   Paul Sandman, M.S














                             The Systematic Evaluation
                                        and Repair of
                                  Failing Drainfields in
                               the Coastal Zone Area of
                                             Virg!      a



















              By: Donald J. Alexander, M.S.
                    Calvin Jones
                    Paul Sandman, M.S










                                               Acknowledgements

                    This manual was funded in part, by, the Virginia Council on the Environment's
              Coastal Resources Management Program through Grant #NA170ZO359-01 of the National
              Oceanic and Atmospheric Administrations, Office of Ocean and Coastal Resource
              Management, under the Coastal Zone Management Act of 1972 as amended.




































                                        First Printing September 25, 1992











                                                    The Systematic Evaluation
                                                          and Repair of
                                                      Failing Drainfields in
                                                     the Coastal Zone Area of
                                                             Virginia


                                                        Table of Contents




                        Acknowledgements      ..........................................           i


                        Table of Contents   ...........................................            ii


                                                            Chapter 1
                                                           Introduction


                        Treatment    .................................................             3


                        Biological Contaminants    ......................................          3
                               Bacteria
                               Viruses


                        Physical and Chemical Contaminants     ............................        5
                               BOD
                               Suspended solids
                               Nitrates


                                                            Chapter 2
                                                        Causes of Failure


                        Causes of Hydraulic Failure    ....................................        7
                               Loading rates
                               Leaking fixtures
                               Uneven distribution










                          Physical Causes of Failure   .....................................            9
                                 Tree roots
                                 Age and material failure
                                 Soil clogging


                          Landscape Position Related Problems     ............................          10
                                 Infiltration


                          Soil Related Causes of Failure . .................................            10
                                 High water table
                                 Slow infiltration rates
                                 Plastic clays
                                 Restrictive horizons




                                                               Chapter 3
                                                         Systematic Approach
                                                     to Evaluating System Failures



                          Introduction  .............................................               :. 13


                          The House and Plumbing    . .....................................             14
                                 Sewer line blockages
                                 Leaking fixtures


                          Septic Tank   .................................................               16
                                 Maintenance
                                 Records and history


                          Drainfield and Distribution Box(e5)   ..............................          18
                                 Trees
                                 Soil conditions


                          Closing Perspectives   .........................................              19












                                                           Chapter 4
                                                        Repair Strategies


                      Introduction . ...............................................                21




                      General Concepts  . .........................         ..................      21
                              Hydraulic loading rate
                              Water use reduction
                              Passive water saving devices
                              Active water saving measures
                              Shallow placement
                              Grey water separation
                              General comments on failing systems



                      Addressing hydraulic overloading   ................................           25
                              Uneven distribution
                              Leaking fixtures
                              Surface water and other sources


                      Addressing physical causes of failure  .............................          27
                              Broken, blocked or damaged components
                              Tree roots
                              Improper venting


                      Addressing problems with landscape position     ......................        28
                              Systems in a concave position


                      Addressing soil related problems    ................................          29
                              Water table
                              Slow percolation rates
                              Plastic clays
                              Soil clogging
                              Restrictive horizons






                                                               iv










                                                       Chapter 5
                                                   Component functions


                     Pretreatment methods and Appurtenances    ........................      34
                            Septic tank
                            Dual septic tanks
                            Sand Filters
                            Aerobic Pretreatment
                            Constructed Wetlands
                            Tees
                            Zabel filter
                            Vent Pipe



                     Final Treatment and Disposal Methods and Appurtenances  ............    41
                            Drainfield
                            Dosed systems (enhanced flow)
                            Low Pressure Distribution
                            Elevated Sand mounds
                            Drip disposal or trickle irrigation
                            Distribution Bo:k
                            Flow diversion valves


                     Privies and Black Water Disposal Devices .........................      50
                            Composting toilets
                            Vault privies

















                                                            v










                                                             Chapter 1


                                                           Introduction


                                Historically, drainfield repairs have not received the attention they deserve.
                        Considered as messy and foul smelling work, drainfield repairs often have been
                        held in low esteem. In some localities repairs have been relegated to the newest
                        environmental health specialist. To be consistently effective, repairs must receive
                        in depth evaluation and consideration before a repair permit is issued.


                                Identifying the cause of failure is an essential element which needs to occur
                        before selecting a method of repair. This has not always occurred. The
                        unfortunate result has been the permitting of new systems which will likely fail
                        because the cause of the failure was never accounted for. In other cases, systems
                        have been replaced that did not need to be replaced. A $2,500 repair system is
                        installed (and will soon fail) when the real culprit is a leaky toilet valve that can
                        be fixed by the homeowner for under $20.00.


                                The purpose of all on5ite systems is to treat and dispose of effluent. Most
                        systems are recognized to be failures when they no longer can dispose of effluent.
                        Rarely have systems been considered as failing when they were polluting ground
                        water. Most systems that are not disposing of effluent are also failing to treat it as
                        well. In many instances, the failure to effectively treat the effluent has occurred
                        long before the system ceases to dispose of effluent.


                                From a public health perspective, sewage treatment is at least as important
                        as disposal. This manual is intended to provide the specialist with guidance on
                        how to evaluate and repair failing drainfields. The manual consists of four major
                        sections. The first section addresses the causes of failures to familiarize
                        environmental health specialists with the scope of reasons why drainfields fail.
                        The second section provides a systematic approach to identifying the cause of a
                        specific failure. The third section addresses strategies to repair systems in a
                        manner that will improve treatment and disposal under the Department's current
                        mandate to protect public health and the environment. The fourth section










                       addresses system components and looks at their application in repairing a failing
                       system. In general, the manual emphasizes pretreatment and water use
                       management.


                              Not every site has a perfect solution. This manual does not pretend to have
                       a solution to every problem. However, after the limits of a site are recognized,
                       essentially every site can be managed to give improved levels of effluent treatment
                       and disposal. The expense and life style changes associated with some repair
                       systems may not make the solutions attractive on a.widespread basis. While these
                       repairs are not acceptable for new construction, they may be preferable to vacating
                       an existing dwelling.


                              The goals of this manual are as follows:


                                     1. To protect and enhance public health protection by providing
                                     thorough and appropriate solutions to repair failing sewage systems.


                                     2. To provide for cost effective, long lasting sewage system repairs.


                                     3. To provide environmental health spe@cialists with the knowledge
                                     to make competent repair decisions and to communicate this
                                     effectively to homeowners.


                                     4. To meet the needs of our customers (citizens with failing
                                     drainfields) through the delivery of our services.



















                                                                2












                       Treatment


                              Wastewater is comprised of many constituents. Some of these must be
                       removed or rendered harmle5s before the water is disposed of to be used again.
                       This is what treatment is all about.


                              Treatment is a relative term and often means different things to different
                       people. What may be considered as sufficient renovation for one person may be
                       entirely inadequate for another person. For example, sewage entering the septic
                       tank is 99% water in most residential sewage. While it is nearly "pure" water, it
                       certainly isn't safe. Effluent from the septic tank can be treated by several means
                       to reduce bacteria levels by another 99%. While this sounds like a high level of
                       treatment, it does not mean the water is anywhere approaching drinking or
                       swimming water quality. Effluent leaving the septic tank typically contains 10' or
                       more fecal organisms per 100 ml. A 99% reduction is equal to a two log reduction
                       and results in 106 fecal organisms per 100 ml. In more familiar terms, this water
                       contains between 10 million and 100 million, fecal organisms per quart. This is
                       hardly "pure" and certainly is not an acceptable level of treatment for human
                       consumption according to any public health standard.



                       Biological Contaminants


                       Bacteria


                              Domestic sewage contains a variety of organisms including bacteria, viruses,
                       and parasites. Some of these organisms, but by no means all, can cause disease.
                       These disease causing organisms are called pathogens. The presence of these
                       harmful organisms is measured indirectly by testing for fecal organisms. Fecal
                       organisms represent a health hazard and indicate the probable presence of disease
                       causing organisms. Wastewater treatment should be designed to remove this
                       potential.


                              Fecal coliform and fecal streptococcus bacteria are commonly found in
                       wastewater. These bacteria live in the intestinal tracts of healthy humans (and
                       other warm blooded animals). Both bacteria are used as indicator organisms to
                       establish whether a source of water is contaminated by sewage. The ratio of fecal
                       streptococcus to fecal coliform can be used to indicate whether the source of


                                                                3










                       contamination is human or animal. The test however lacks sensitivity. More
                       often than not the results of the ratio are ambiguous and unable to differentiate
                       between sources. Usually, the fact that water is contaminated is more important
                       than the source.


                               In terms of treatment, residential wastewater usually contains 10' to 1010
                       organisms per 100 ml. The septic tank provides little or no improvement in the
                       biological quality of the effluent. Biological treatment of effluent occurs in the
                       aerated soil beneath and around the drainfield. Harmful bacteria from the
                       wastewater must compete with nativesoil bacteria and organisms in the biomat
                       around the trench. Those organisms that pass through the biomat at the gravel-
                       soil interface must be physically filtered by the soil or die off due to time and
                       hostile environmental conditions in order to render the wastewater harmless.
                       From a public health perspective, this must occur before the wastewater is used
                       again by humans.


                               Most pathogenic organisms have a narrow range of environmental
                       conditions under which they can survive. The warm, wet, anaerobic environment
                       of the intestines is ideal for the survival of these organisms. The colder, dryer,
                       aerobic environment of a well drained soil is usually unsuitable for the
                       reproductive and survival needs of these organisms.


                       Viruses


                               Viruses are much smaller than bacteria and soil particles. They are not
                       physically filtered by soil. They are however, retained by the soil using a very
                       different mechanism. Soils have a property known as cation exchange capacity
                       (CEC). This refers to the soil's negative electrical charge and ability to hold
                       positively charge particles. The positively charged viruses then attach to
                       negatively charged soil particles as they move through the soil. This process is
                       called adsorption. Cation exchange capacity is dependent upon the chemical make-
                       up of the soil and the available surface area of the soil. That is to say, the CEC of
                       a clayey soil will almost always be higher than that of a sandy soil.


                               Viruses consist of a nucleic acid (either RNA or DNA) and a protein coating.
                       The protein coating is positively charged and because of the organisms extremely
                       small size, it will be adsorbed to the negatively charged particles in a soil. As a
                       result, it should be evident that a significant clay fraction (even that found in


                                                                  4










                       texture group II soils ) is necessary for optimum effluent treatment. Sandy soils
                       can treat bacteria well, while allowing viruses to pass essentially unaltered.



                       Physical and Chemical Contaminants


                       Biochemical Oxygen Demand


                               One of the measures commonly employed when evaluating wastewater is
                       the five day biochemical oxygen demand test or BOD,,. This test is used to
                       measure the strength and biological stability of wastewater. It does this by
                       measuring how much oxygen must be consumed to biologically digest and
                       chemically stabilize the organic components of the wastewater. Typical residential
                       wastewater has a BOD,, between 200 and 250. In and of itself, BOD, is of no
                       public health significance. It does however, provide a tool for defining the
                       characteristics of a particular waste flow. This can then be used to establish
                       appropriate treatment methods.


                       Suspended Solids


                               Suspended solids in septic tank waste typically are the result of material
                       close to the specific gravity of water. Consequently they do not settle out in the
                       less than perfect settling basin called the septic tank. Suspended solids include
                       filamentous material, hair and biological wastes.


                               It should be noted that suspended solids in the septic effluent do not contain
                       much BOD. Most of the BOD is dissolved in the liquid portion of the effluent. The
                       major problem with high suspended 5olids in effluent is the physical clogging of
                       pumps, LPD orifices, and soil pores in the absorption field.


                       Nitrates


                               Nitrogen is generally considered to be the single most important chemical
                       constituent in domestic wastewater. From a public health aspect excess nitrates
                       can cause methemoglobinemia. Environmentally they can cause eutrophication in
                       streams and rivers and are also the limiting nutrient in salt water estuaries.





                                                                  5










                                Nitrates in domestic wastewater are produced almost entirely as a result of
                         the conversion of the nitrogenous wastes in urine to ammonium and then to
                         nitrate. In the presence of a carbon source in an anaerobic environment, the
                         nitrate can be reduced to nitrogen gas and carbon dioxide. The typical situation
                         has the nitrogenous wastes being converted to ammonium in the septic tank and
                         then to nitrate in the aerobic environment of the drainfield. Nitrates are highly
                         soluble in water and do not bind to soil. As a result, nitrates are highly mobile.


                                At levels in excess of 10 mg/l nitrates may cause "blue baby syndrome"
                         (methemoglobinemia) in infants. Infant hemoglobin has a higher affinity for
                         nitrate than for oxygen. Infant hemoglobin is replaced by adult hemoglobin as the
                         child grows. By the age of six months, the replacement is sufficiently complete
                         that the occurrence of "blue baby syndrome" is unlikely or impossible. The result
                         of this illness is that infants essentially suffocate because their blood can no longer
                         carry oxygen (Baum, 1982).


                                While this is a very serious, potentially fatal, condition, it is by no means
                         common. Reasons for this are that nitrate levels from septic systems generally will
                         not exceed 10 mg/l in the ground water except where unusually high development
                         densities occur. The Virginia Department of health requires the designers of all
                         systems with design loading rates in excess of 1,200 gallons per acre to address
                         nitrate contamination in the ground water. Even if the 10 mg/1 limit is exceeded,
                         there is no guarantee a case of blue baby would occur. Prior to the illness
                         occurring, a drinking water well inust intercept the contaminant plume from the
                         drainfield and a susceptible infant under the age of 6 months must consume
                         quantities of the water sufficient to cause the illness.


                                It is important to note that onsite wastewater systems are but one of
                         several significant contributors of nitrates to ground water. Agricultural fertilizers,
                         animal wastes (especially when concentrated in areas such as feed lots), and
                         residential lawn fertilization all can be sources of nitrogen. Of the potential
                         sources of nitrogen, residential onsite systems are generally the least significant
                         contributor, but nonetheless should be considered.









                                                                    6








                                                            Chapter 2


                                                      Causes of Faflure




                               Before a strategy to correct a malfunction can be developed the problem
                        cause must be identified. The causes for the failure can be varied and might be
                        attributed to a number of different factors. Four primary reasons exist for system
                        failure. These are: hydraulic overloading, physical component failure due to stress
                        or deterioration, landscape position which contribute excess water to the absorption
                        field and unsuitable soil conditions.




                        Causes of Hydraulic Failure


                               Hydraulic failure occurs when more effluent is applied to an absorption field
                        than can be disposed of by the field. Hydraulic failures express themselves as
                        continuous or seasonal wetness over the drainfield. There are several causes of
                        hydraulic failure but all are related to either excessive loading rates, organic
                        clogging or a combination of the two. In addition to the obvious health and
                        nuisance problems associated with surfacing effluent, some limited and inadequate
                        wastewater disposal may also be associated with this type of failure.


                        Loading rates


                               The hydraulic conductivity of a soil will dictate the acceptable hydraulic
                        loading rate for a given site. Long term acceptance rates (LTAR) are normally
                        significantly less than measured short term rates. Loading rates are generally
                        construed to mean the number of gallons of effluent applied per square foot of
                        absorption area. In this manual, the loading rate is the number of gallons of
                        effluent and water from all sources applied per square foot of absorption area. One
                        of the key strategies to repair many systems is to eliminate all extraneous wa   ter
                        and thereby prevent it from being applied to the absorption field.


                               Excessive loading rates are probably the leading cause of drainfield failure.
                        This type of failure may be caused by excessive water use by the individuals



                                                                  7










                       occupying the house or an excessive number of occupants in a house. The end
                       result is, water use exceeds the design capacity of the sewage disposal system.


                              The causes of excess water use are as varied as the residents of the
                       Commonwealth. In some upscale neighborhoods hot tubs and Jacuzzi's have
                       contributed to hydraulic failures. Informal conversations with field staff and
                       consultants indicate that this may be a growing problem. Additionally, other uses
                       such as a small scale commercial laundry, a beauty shop, or even hobby related
                       uses such as darkroom processing can lead to premature system failure. Even
                       illness can affect water use. One of the authors has observed a failure due to
                       waste from a kidney dialysis machine over-loading an older, undersized drainfield.
                       During the investigation of the failure the homeowners should be interviewed to
                       determine what water use patterns are occurring and if any additional loads are
                       being place on the system for which it was not designed.


                       Leaking fixture5


                              One prime cause of hydraulic failures is leaking plumbing fixtures.
                       Whether it is a sink or bathtub with a steady drip or a toilet that never stops
                       running, awareness of the problem and its implications is low. These leaks are
                       often neglected until the problem surfaces in the yard. A small leaking facet or
                       toilet can easily add the equivalent of an extra bedroom to the daily waste flow.
                       More serious leaks, or multiple leaks, can double the estimated the estimated
                       wastewater flow.




                       Uneven distribution


                              Uneven distribution of effluent in the drainfield may result in premature
                       failure of the soil absorption system. Conventional sewage disposal systems use a
                       distribution box to equalize the flow to the drainfield. Under near perfect
                       conditions, equal distribution is difficult to achieve using a distribution box. The
                       resulting uneven flows may or may not be significant enough to cause any
                       problems with systems installed on flat terrains. On the other hand systems
                       installed on sloping terrains may develop problems should the downhill lines
                       receive more water than the other lines of the system. The problem may be
                       compounded if care is not taken to prevent the box from being disturbed during the
                       back-filling process.


                                                                 8










                     Physical Causes of Failure


                     Tree roots


                            When the drainfield is located in or near a wooded area, tree roots may
                     cause problems. Trees with shallow root systems will seek water from the
                     drainfield lines. A network of roots can enter in the drainfield and grow back to
                     the distribution box and septic tank blocking the flow into the drainfield. Maple
                     trees, alders and other water loving species should be considered as possible
                     sources of roots entering a system even when located 100 or more feet away from
                     the problem area.


                     Age, physical disturbance and material failure


                            Some components will outlast the useful life of the system while other
                     components deteriorate over a shorter period of time. Components such as
                     Orangeburg pipe, cast iron septic tank tees and some concrete products are system
                     elements that tend to fail early. Plastic pipe, plastic distribution boxes and some
                     concrete may never deteriorate (significantly) with age but, like any product, can
                     be damaged when stressed. Driving over system components, plowing or tilling
                     over a system and other disturbances such as utility installations can damage
                     components.


                     Clogging or organic mats


                            Clogging mats are another cause of failure and are associated with older
                     systems and systems that have received poor maintenance or abuse. An organic or
                     zoogleal mat will form on the soil gravel interface of all properly working systems.
                     Without any other external factors, over time, even the best soils cease to absorb
                     effluent quickly enough to keep up with wastewater production.


                            Use and maintenance can either retard or accelerate clogging. One of the
                     prime accelerators of mat formation is the garbage disposal. Use of a garbage
                     disposal increases the organic loading rate placed on the system. Compounding
                     the problem is that a significant portion of the solids are composed of cellulose,





                                                               9










                       which is resistant to biological breakdown in the septic tank. Additiona lly, any
                       water use which scours the tank, such as discharges from hot tubs or Jacuzzi's,
                       will increase the organic loading rate placed on the drainfield.



                       Landscape Position Related Problems


                       Infiltration


                              All onsite sewage disposal systems are susceptible to ground water
                       infiltration if the septic tank and pump chamber have not been properly sealed.
                       This occurs most frequently when the house is built low on a slope. The resulting
                       position of the septic tank and pump chamber is such that they are likely to be
                       placed in an area with a high seasonal water table. When the pump discharges,
                       emptying the pump chamber, surface water can flow directly into a leaky pump
                       chamber or enter from leaks in the septic tank. In essence, the pump chamber and
                       septic tank serve as a means of dewatering the area where they are installed. This
                       will result in hydraulic loading rates on the drainfield greatly in excess of the
                       design rate.


                              The placement of the septic tank and pump chamber in a drainway may
                       also result in the sewage disposal that disposes of surface water which has been
                       directed toward the tank or pump chamber. Inadequate or improper surface
                       drainage may be another contributing factor to hydraulic overloading- Careful
                       attention should be paid to surface drainage, footing drains and roof run-off in the
                       vicinity of the drainfield. The removal of surface water and the diversion of footing
                       drains and roof run-off will lessen the amount of water which must be disposed
                       into the drainfield.




                       Soil Related Causes of Failure


                       High water table


                              High seasonal water tables are another cause of failure for a sewage
                       disposal system. High water tables usually occur because naturally occurring site
                       and soil conditions cannot dispose of precipitation falling or flowing onto the site.
                       The wastewater from a home will compound the problem. The most significant


                                                               10










                       problem with high water table soils is the greatly reduced treatment efficiency of
                       the soil. Renovation of effluent in saturated soils requires much greater time and
                       distance than treatment in unsaturated soils (Reneau and Pettry, 1975).


                               Soils having drainfields installed in a seasonal water table will also have a
                       difficult time properly disposing of both the naturally occurring precipitation and
                       the added wastewater. These system will experience anaerobic conditions in the
                       drainfield resulting in the formation of a biological mat and soil reduction
                       processes sooner than systems installed in well drained soils. In areas of high
                       water tables the life of a sewage disposal system will usually be much shorter than
                       in areas with well-drained soils.


                       Slow infiltration rates


                               Soils with slow infiltration rates may exhibit yellow and red mottles, pale
                       brown coatings on soil ped faces and root channels and may occasionally show grey
                       mottling. These observed soil characteristics indicate that the soil is having
                       difficulty transmitting the amount of precipitation infiltrating in the immediate
                       area. Typically in Virginia this is about 40 inches per year. Adding a drainfield to
                       the site will typically add an equivalent of 120 inches or more of rainfall per year.


                               Treatment and disposal in these soils varies with seasonal rainfall. In the
                       spring and fall when rainfall is high, treatment will deteriorate. This occurs after
                       periods of prolonged saturation, which routinely happens late in the winter and
                       through the spring, until leaf out occurs. When the water table is high, both
                       wastewater treatment and disposal become serious problems. These soils are
                       responsible for most seasonal failures.


                       Plastic clays


                               Plastic clays or high shrink-swell soils generally do not provide any
                       acceptable level of treatment and disposal. These soils contain active clays, such
                       as montmorillonite, which expand when wet and shrink when dry. When a
                       drainfield is installed in shrink swell soils, effluent causes the clays to swell shut
                       and failure is inevitable.












                        Restrictive horizons


                               Restrictive horizons impede the downward movement of water. They may
                        also be the cause of "perched" water tables. Their impact on the operation of a
                        drainfield depends on several factors. Their proximity to the trench bottom, their
                        degree of permeability, and their continuity all contribute to their relative
                        importance. The closer a restrictive layer is to a drainfield and the less permeable
                        it is the greater the adverse impact of the restrictive horizon. Additionally, some
                        types of restrictions may not be continuous across a drainfield site. Fragipans in
                        some parts of the state are extremely discontinuous. The practical result of a
                        discontinuous restriction is to make the functional portion of the drainfield too
                        small unless the restriction is accounted for in the system design.




































                                                                 12








                                                       Chapter 3


                         Systematic Approach to Evaluating System Failures




                    Introduction


                           Septic tanks and drainfields have been described as a temporary means of
                    sewage disposal. Some systems last for many years when installed under favorable
                    conditions; however, even those systems will eventually fail. Other systems may
                    experience premature failures due to hydraulic loading, soil conditions, or a
                    number of other external factors.


                           No matter what the reason for a system failure, the health department will
                    be involved with correcting the problem. There will be far greater pressure on the
                    environmental health specialist to provide a correct solution than if he or she were
                    evaluating a vacant lot. There may be poor soil conditions, inadequate space, and a
                    number of other factors making a proper solution far more difficult. The property
                    owner with a considerable amount of money invested will expect the specialist to
                    provide answers to correct the sewage disposal problems. The health department
                    may not have the answers to all the problems, but we owe it to the homeowner to
                    provide the best advice possible. This can be done this by using a systematic
                    approach in evaluating the problem.


                           The key to correcting any problem is the proper diagnosis of the cause of the
                    problem. In the case of a leaking toilet, adding drain lines to cure the saturated
                    drainfield, will provide very short term relief. If the cause of the problem is not
                    addressed, the problem will reoccur. Be careful not to fall into the trap of
                    assuming the cause of drainfield failure before thoroughly investigating the
                    situation. Failure to use a systematic approach could result in an embarrassing
                    situation for the specialist and unnecessary expense for the homeowner. Take your
                    time and use good common sense when evaluating an onsite sewage disposal
                    system problem.


                           In making a systematic evaluation of the problem there will be three major
                    component areas to consider. The first part of the evaluation will consist of the
                    house, plumbing, and hydraulic loading. The second major component area will be


                                                            13










                        the septic tank and appurtenances (tees, sewer line and effluent line). The third
                        and final component area will be the distribution box and drainfield. When
                        making an evaluation it is important to start with the house and plumbing and
                        work toward the drainfield. Following this approach will assist the specialist in
                        identifying the source of the problem and providing the best lead in finding an
                        appropriate solution.



                        The House and Plumbing


                               Starting in the house, survey the occupants of the house and make an
                        estimate of the amount of water being generated by the household. If the house is
                        connected to a public water supply, actual water use figures should be obtained. In
                        a rural setting this will probably riot be possible. However, in such a case, the flow
                        can be estimated by asking a few simple questions. The first thing to address is
                        the number of occupants in the house. This will yield a fair indication of what the
                        base household water use is in gallons per day (GPD). Next, it is necessary to
                        determine if there are any other unusual uses that would modify the base
                        estimate. They may be operating a business or have a hobby which would
                        generate additional water use. Instances have occurred where day care centers
                        and small scale laundry services have been operated out of residential dwellings.
                        Determine what type of fixtures and facilities are in the house. Fixtures such as
                        hot tubs, jacuzzi's, and garbage disposals are all items which contribute to
                        increased water flows and in some cases increase the organic load placed on the
                        drainfield. Determine if any type business is being operated out of the home such
                        as a beauty shop, or maybe they have a darkroom. By questioning the occupants
                        regarding the type of uses placed on the system, a reasonable assessment of water
                        use can be made.


                        Sewer line blockages


                               While inside the house, evaluate the extent of any plumbing back-ups.
                        Determine if the problem is occurring with all fixtures in the house or a single
                        fixture. There have been cases where people have called the health department
                        because one toilet will not flush while all other fixtures in the house are working
                        satisfactorily. This usually indicates a blockage in the plumbing which can be




                                                                 14










                        repaired with comparative ease. On occasion, toys, diapers or other items have
                        been known to completely block the sewer line causing all fixtures in the house to
                        back up.


                               In some instances the kitchen drain may have become stopped-up due to
                        grease. Occasionally the kitchen and laundry drains have been connected to a
                        grease trap which is separate from the rest of the septic tank system. If the
                        problem can be isolated to one fixture, or a common group of fixtures, the
                        homeowner may need a plumber and not a septic tank contractor. Assure that the
                        sewer line is open before proceeding further with the evaluation.


                        Leaking fixtures


                               Another essential element that the specialist must check for is leaking
                        toilets or fixtures. The leaking toilet is one of the most common and overlooked
                        causes of unintended water waste. Be sure to ask the homeowner if they have any
                        toilets which "hang-up" or "run-on" after being flushed, or in some way do not do
                        not operate properly. Because homeowners are not always aware of these
                        problems, the specialist should ask to re-check all the toilet fixtures. One way of
                        checking a toilet for leaks is to put a drop of food coloring or vegetable dye in the
                        toilet tank and wait ten minutes to see if it leaks into the bowl. If the coloring
                        leaks into the bowl, the plunger ball in the toilet is the most probable cause of the
                        leak. The homeowner needs to check the plunger ball to see if it is obstructed with
                        grit or debris at the seal or if the seal is worn and needs to be replaced.


                               Ask the homeowner about leaking faucets or faucets that are difficult to
                        shut-off. Ask permission to double check these. This can be conveniently done
                        while checking for leaking toilets. A plumber should replace the washers on
                        dripping faucets. Either a leaking toilet or faucet can increase wastewater flows
                        sufficient to cause system failure. Be sure to thoroughly investigate the home for
                        leaks before proceeding further with the evaluation.











                                                                  15










                   Septic Tank


                   Maintenance


                         Once the hydraulic loading rate has been established and the house fixtures
                   and plumbing eliminated as a problem, determine how well the system has been
                   maintained. When was the last time the septic tank was pumped and how often
                   has the tank been routinely pumped. If the tank has to be pumped frequently
                   during the winter months, the drainfield may be installed in soils with a seasonal
                   water table or in slowly permeable soils.


                   Records and history


                         Obtain as much history as possible on the system. Often, the past
                   performance of the system can shed some light on current problems. Did the
                   system malfunction gradually or did it occur suddenly? Be very suspicious of
                   failures that occur suddenly without warning. These types of failures usually occur
                   when a component fails or the water use increase sharply. A gradual failure is
                   more likely an indicator of system failure in the drainfield. This type of failure
                   may start out as a small wet area in the yard that gradually increases in size. If
                   drain lines are added to a sudden failure, without correcting other problems, the
                   problem may reoccur. The environmental heath specialist should review the
                   health department records of the system design and discuss the history of previous
                   problems with the homeowner. Department records should indicate the design
                   capacity of the system, general design, system location, and the age of the system.


                         When records on a system cannot be found there are several other visual
                   and me'chanical ways to locate the system components. The septic tank is
                   normally (but by no means always) located near the house where the main sewer
                   line exits the house. This can be located by looking in the crawl space or
                   basement. When access inside the house is limited, locating the vent pipes on the
                   roof can help locate general plumbing locations. It then becomes a matter of
                   second guessing what a plumber might have, should have or could have done to get
                   the plumbing outside. The5eptic tank is usually located in the shortest line '
                   between the house and the drainfield. The drainfield can often be identified by the
                   deeper green color over the trenches and sometimes by settling over the trenches.
                   Additionally, look for unusual lawn growth to assist in locating the tank. A



                                                    16










                        leaking tank may give rise to lush growth, while a tank with minimal cover may
                        not support grass well at all. With some regularity, the exact shape of the tank is
                        revealed in the lawn.


                               When all else fails, don't hesitate to have the homeowner hire a plumber or
                        septic tank pumper locate the system components. Experienced professional are
                        equipped to snake out component locations and are more adept at probing and
                        locating the parts of a septic system than most environmental health specialists.
                        Often times they have been to the site several times before the health department
                        is called for assistance. Use these individuals as a re5ource and learn what has
                        been done to repair the system.


                               After the components are located, the environmental health specialist
                        should request the owner to have the septic tank and distribution box uncovered to
                        evaluate these key components. The tees in the septic tank are essential elements
                        of the system and cannot be checked any other way. Older systems were usually
                        installed using cast iron tees. Cast iron tees will corrode and stop up. This can
                        happen at either the inlet or outlet tee. Septic tank pumpers have been known to
                        removed these tees to snake out the conveyance line. All too frequently they do
                        not get replaced. One should therefore note if the tank still has both tees.


                               If the tank has been pumped recently, it is often wise to solicit information
                        from the septage hauler. Often they can offer observations about the system, such-
                        as water flowing back into the tank or other unusual conditions, that earl aid in
                        identifying the problem. With the tank uncovered the specialist can observe the
                        liquid level in the tank. If the liquid level is at normal flow level, but the owner
                        cannot use the fixtures in the house, check the inlet side of the tank. This
                        condition indicates a blockage in the sewer line or the inlet tee. If the septic tank
                        is overflowing at one of the access lids the outlet tee should be checked. The most
                        probable cause of this condition is a clogged outlet tee or eMuent line between the
                        tank and the distribution box. If the outlet tee is clogged, the drainfield may not
                        need to any repair.


                               The conveyance line from the septic tank to the distribution box is another
                        area where problems may occur. Many older systems used Orangeburg pipe for
                        the conveyance line when they were installed. Orangeburg pipe is made of tar and
                        paper rolled into a pipe. This type of pipe can blister on the inside and close the
                        line off. It is no longer used today and should be replaced whenever a system is


                                                                  17










                       repaired. Regardless of the material used, the conveyance line may have been
                       damaged when the system was backfilled, when the yard was landscaped or at
                       some later date. Be sure to look for evidence of traffic use over the system. This is
                       especially important in the spring when the ground is wet and cannot bear as
                       much weight. This is when traffic damage is most likely to occur.



                       Drainfleld and Distribution Box(es)


                              The next step is to uncover and examine the distribution box. If the water
                       is at normal flow level (even with the bottom of the outlets), the problem should be
                       back towards the house or the hydraulic failure is occurring at a lower elevation.
                       On the other hand, there are several possibilities if the outlet ports are covered
                       with effluent. Some potential problems are drainfield failure due to clogging, a
                       high seasonal water table, poor soil permeability, tree roots (or other blockage) in
                       the header lines, or other problems.


                              Investigating the drainfield area is next step in the process. This should
                       include a soil evaluation performed in the drainfield area. If all else is working
                       properly, it is assumed that the drainfield will be saturated. A boring or two
                       should confirm this in short order. If the drainfield is not saturated, the problem
                       is either in the header lines or has been missed and lies somewhere back toward
                       the house. If the drainfield is saturated, the next question to be answered is why?


                       Surface drainage and other water sources


                               The saturation may be caused by improper area drainage. Included in the
                       drainage evaluation would be roof and footing drains which may be directed on the
                       drainfield area. Excess drainage from swimming pools, hot tubs and water
                       softeners may be adding excess water to or over the system. Surface water
                       management is equally important. Does the area have positive surface drainage or
                       does water collect over the drainfield? Are there paved areas generating a large
                       amount of surface run-off onto the site? Are there electric, gas, cable TV or other
                       underground utilities which may divert off site water into the drainfield? Is there
                       a lawn irrigation system is used excessively? Are there any old water lines that
                       may cross the drainfield area? Older water lines were often galvanized and tend
                       to develop pin hole leaks which could flood a drainfield. Has the owner planted
                       trees in the drainfield area?



                                                                 18










                              If the sewage disposal system has a pump, a leaking septic tank or pump
                       chamber must be considered. Typically you may find the house, septic tank, and,
                       pump chamber located in an area with a high seasonal water table and the
                       drainfield in a remote area where soil conditions are better drained. If the septic
                       tank and pump chamber have not been properly sealed ground water will leak into
                       them. When this happens a hydraulic overload could be created by this additional
                       water. The environmental health specialist should be aware this possibility exists
                       when evaluating a drainfield problem.


                       Trees


                              Roots from trees have also caused septic system problems. Explain to the
                       owner the effects of trees on the septic tank system. Encourage the owner to
                       remove all trees with shallow root systems from the drainfield area. Water loving
                       species such as maples, alders and willows should be removed from more than just
                       the immediate area over and in close proximity (ten feet) of the drainfield. It is
                       suggested that these trees be kept at least fifty feet away and further is better.


                       Soil conditions


                              Poor soil conditions as well as age can cause a drainfield to become ponded.
                       Soil conditions which can cause failure have already been briefly discussed. It is
                       important to note that even good soils will clog over time and cease to operate
                       satisfactorily. These systems are typically twenty-five years old or older, and
                       exhibit a dark gray or black mat at the edge of the drainfield-soil interface. Soil
                       boring5 in the drainfield area and in the drainfield itself are essential to determine
                       the cause of failure. As with any soil evaluation, it is essential to keep good notes
                       on the observations made while boring.



                       Closing perspective


                              If you are lucky enough to have the homeowner(5) present, take time to
                       educate them on how to properly care for a septic tank system. Let them know
                       there is a difference between a city sewer system and a septic tank system.
                       Provide pamphlets which outline the care and maintenance of the septic tank when
                       the operation permit is issued. The more the owner knows about the septic tank
                       system the greater the chances of it being maintained and working longer.


                                                               19










                             The most important aspects of making a good evaluation are using common
                      sense, good judgement and following a systematic approach. However, simply
                      knowing what caused a failure is only the fir5t step in solving the problem. Once
                      the problem has been properly identified, an appropriate solution to the problem
                      must be developed to correct the problem.











































                                                              20









                                                         Chapter 4


                                                    Repair Strategies


                      Introduction


                             This section of the manual is intended as a starting point for finding
                      solutions to failing drainfields. Environmental health specialists looking for a
                      panacea or a definitive answer to every problem will be disappointed. They don't
                      exist. Almost every site can be improved upon. Many sites can be repaired to the
                      satisfaction of all parties, while other sites can only be managed to reduce potential
                      health risks. A careful review of the strategies in this section will help the
                      specialist distinguish between the repairable and the managetLble and to choose an
                      appropriate course of action.


                             Once the problem with the sewage disposal system has been diagnosed a
                      strategy for the correct repair must be developed. It is very important to properly
                      identify the cause of the problem before making a recommendation to correct it.
                      Strategies may differ based on the nature of the problem or combination of
                      problems. The approach to correct a seasonal problem may be entirely different
                      than the strategy used to correct a 30 year old system failing due to organic
                      Clogging. Both treatment and disposal of the effluent must be considered when
                      developing a method of repair. If treatment can be achieved and is economically
                      viable, it should be accomplished.


                      General Concepts


                      Hydraulic loading rate


                             Hydraulic infiltration decrease as systems age while loading rates tend be
                      constant or increasing. Organic clogging, prolonged anaerobic conditions, high
                      carbon-nitrogen ratios, high BODs and suspended solids all contribute to
                      accelerated reductions in infiltration rates (Avnimlelech and Nevo, 1964 and
                      Kristiansen, 1982). A reduction in the hydraulic loading rate or flow in some cases
                      will provide a viable repair option. Dosing the system will enhance aerobic
                      conditions within the system by providing alternating periods of wetting and
                      drying. Reducing flow will also enhance the ability of the system to operate under


                                                               21










                        aerobic conditions by reducing the amount of liquid to be disposed of. The
                        advantages of dosing are negated when done in conjunction with systems installed
                        in a water table because these systems will remain flooded. In order for dosing to
                        be effective, an aerobic period is necessary.



                        Water use reduction and management


                               Water management is the key to drainfield longevity and assuring effective
                        system repairs. Water use reduction may be broken down into two major classes:
                        active and passive. Active water use reduction requires changes in lifestyle and
                        water use habits. Passive water use reduction requires the installation of water
                        saving fixtures and does not appreciably alter the users lifestyle.


                               Water use reduction can be achieved by installing water saving devices.
                        These items can be purchased from many hardware stores, plumbing suppliers and
                        home centers. Some may even be installed by the homeowner. The simplest of
                        these would be water saving shower heads, aerators for faucets, and water
                        displacement devices that can be placed in the toilet tank. The toilets on the
                        market today typically use 3.5 gallons per flush and water saving toilets are
                        available that use 1.6 gallons. Many new home appliances are designed to reduce
                        water flows when used properly. The use of water saving appliances should be
                        encouraged. In addition to the many mechanical devices available, there are
                        conservation measures the homeowner can apply to everyday living habits to
                        reduce water flows. Local utility departments usually have this type information
                        in booklet form for the public's use.


                        Passive water saving devices


                               Generally these will be the most effective methods of achieving modest but
                        consistent water use reductions. They include the use of water saving toilets,
                        water saving shower heads and in line flow restricting devices, low flow faucets
                        and low water use appliances. Typical toilets today use 3.5 gallons of water.
                        Effective toilets that use as little as 1.6 gallons per flush are available. Flow from
                        shower heads can be reduced effectively to three gallons per minute without
                        5acrificing the quality of the shower. When possible, flow restrictors should be
                        used rather than low flow shower heads. Shower heads are readily replaceable
                        and are not as permanent as in line flow restrictors.


                                                                  22












                        Active water saving measures


                                These are measures that require lifestyle changes on the part of the
                        homeowner. Their effectiveness will be highly variable depending upon the
                        cooperation of the occupants. As soon as there is a change in ownership in a
                        dwelling that's restricting its water usage, there is a high probability that water
                        use reductions will not be continued. These methods are included as educational
                        and informational material. Wherever possible, rely on passive water saving
                        devices. Active water saving methods include the following actions:


                                       1. Exclusive or seasonal use of a laundromat for clothes washing.


                                       2. Modifying when laundry is done at home to avoid peak periods of
                                       water use. Laundry is done throughout the week as opposed to on a
                                       predetermined laundry day.


                                       3. Only full loads of clothes are washed.


                                       4. Showers are closely timed or the shower is not run continuously
                                       while washing (i.e., soak, lather with the water off, then rinse).


                                       5. The dishwasher is not run daily and only run when there are full
                                       loads.


                                       6. Toilets are not flushed after every use.


                                       Compliance with these suggestions is impossible to measure or
                                enforce and the Department is not suggesting that staff attempt to do so.
                                These suggestions are included so that homeowners with especially onerous
                                failurescan be advised how they might manage further water use
                                reductions.




                        Shallow placement


                                Prior to 1982 the emphasis for sewage disposal system design was placed
                        upon the disposal of effluent rather than treatment. Today's strategy is to repair
                        these systems in ways that maximize treatment without sacrificing disposal.


                                                                   23










                        Shallow placement offers the advantages of greater separation distances to the
                        seasonal water table, a greater ability to operate under aerobic conditions, and
                        generally better soil textures.


                               Achieving shallow placement may be as simple as raising the plumbing
                        under the house and where it exits the house or may require the use of a pump
                        chamber and sewage pump. Each of these methods of achieving shallow placement
                        has its own advantages. Raising the plumbing may have more initial economic
                        appeal and avoids all concerns of a mechanical failure of a pump. If a pump
                        chamber and sewage pump is used, the system can be designed for enhanced flow.
                        This type of system provides dosing and resting cycles which improves aerobic
                        treatment.


                               Another strategy which could be employed is the use of an ultra shallow
                        placed low pressure distribution system. This system would offer the advantage of
                        equal distribution over the entire drainfield area. The cost of this system will be
                        slightly higher but it offers a greater longevity. In areas where the seasonal water
                        table is a major concern, a modified sand mound may provide the best solution.


                        Grey water separation


                               Grey water separation can reduce the hydraulic loading on a drainfield.
                        Typical water usage from a clothes washer varies from 30-60 gallons per full cycle.
                        A household with small children will add many gallons of wastewater to be
                        disposed of in the septic tank system. Under the present Sewage Handling, and
                        Disposal Reprulations it is estimated laundry wastewater accounts for 20% of the
                        total wastewater volume. If the grey water were placed on a separate system or
                        eliminated, a minimum 20% flow reduction would be expected on the existing
                        drainfield system. Other sources place this figure even higher. This reduction in
                        water flow could possibly be enough to allow the system to function properly.


                        General comments on failing systems


                               There are few general comments that can be made about failing drainfields.
                        Each is a unique situation calling for individual thought and evaluation. Two
                        general concepts which do seem to have broad application are the use of water
                        saving fixtures and the need to correct problems expeditiously. There is no cause
                        of failure that will not benefit by reducing water flow to the system. Septic tank


                                                                 24









                         efficiency improves and the amount of effluent on top of the ground is immediately
                         reduced. Drainfield failures that are allowed to continue indefinitely are a clear
                         risk to public health. Additionally, in many cases failures that are caught quickly
                         can be fixed easier and at less expense to the homeowner than if they are
                         discovered years later. Drainfields that are allowed to remain continuously ponded
                         undergo soil reduction processes which reduces the ability of the soil to absorb
                         effluent. The sooner a site is evaluated, and a repair strategy is identified, the
                         more likely portions of the system can be returned to service. While timeliness is
                         important, there is no need to rush an evaluation: be thorough, be precise and use
                         good judgement.



                         Addressing Hydraulic Overloading


                                The initial step is to identify and remedy the reason that caused the
                         overload to occur. Damage to an overloaded system can range from minimal to
                         total drainfield destruction. It is important that the specialist judge the extent of
                         the problem and determine how much repair or replacement is necessary.


                                By boring into several of the drainfield trenches in several places along
                         their length, the specialist can determine how much soil reduction (formation of
                         gray mottles) and mat formation (black organic deposits) has occurred within the
                         system. If there is little or no soil reduction, chances are good that the drainfield
                         can recover from the failure without additional repairs. Occasionally it is
                         necessary to block flow to one or more lines temporarily (three to six months) to
                         allow them to recover. When this is attempted, it is essential that the specialist
                         determine that the remaining portion of the system is adequate in both capacity
                         and condition to handle the temporary increase in flow. Additionally, follow-up is
                         equally essential to assure that the rested lines are placed back in service on time
                         to prevent damage to the remainder of the system. A follow-up visit should be
                         made within six months.


                                Systems with significant organic clogging (which should be expected in older
                         systems) that also have significant soil reduction in the trenches should be
                         abandoned. They generally cannot be expected to recover from the failure
                         sufficiently to be useful in a reasonable amount of time (note: in a number years
                         the laterals may "rejuvenate" themselves and be useful again. How long this
                         process will take is the subject of some debate In general, severely damaged


                                                                  25










                       trenches probably need years, not months, in an aerobic environment to recover).
                       Depending upon the severity of -the problem these systems need to be either
                       expanded or replaced. Decisions such as this need to be based on judgement and
                       local experience. There is no substitute for experience.


                       Uneven distribution


                              The most common distribution problem is an out of level distribution box.
                       Frequently, for a variety of reasons, the lowest lateral receives an excessive
                       amount of effluent. Before determining the best method of repair the specialist
                       must determine the extent of damage which has occurred. The techniques for
                       determining this are given in the previous section on hydraulic overloading. In all
                       cases the distribution method must be repaired. In some cases this alone will solve
                       the problem. In other cases laterals may need to be rested or replaced. In extreme
                       cases the entire system may need to be replaced.


                              In marginal soils (rates slower than 60 mpi or soils having a perc rate
                       slower than 30 mpi and a water table within 18 inches of the trench bottom)
                       replacement of the distribution box with a pressure manifold should be considered.
                       This is initially expensive but can be cost effective if, in the long run the drainfield
                       life will be increased. The dosing cycle which alternates aerobic and anaerobic
                       conditions has been suggested to be excellent for prolonging absorption field life
                       expectancy in certain soils. In very good soils and unsuitable soils, the difference
                       in life expectancy may not be justified. A retrofit such as this includes adding a
                       pump chamber and replacing the tight line to the manifold which is located
                       approximately where the distribution box was located.


                              At sites where the expense of a pressure manifold does not appear
                       warranted or feasible, enhanced flow, installation of a flow diversion valve, of even
                       at grade access to the distribution box are alternatives that should be considered.
                       A properly designed enhanced flow system will offer most of the advantages of a
                       manifold distribution system. A flow diversion valve can provide long term
                       alternating and wetting cycles which can benefit the life expectancy of the
                       absorption field. An at grade distribution box, while the least acceptable
                       alternative, can provide a practical means of removing individual lines from service

                       as necessary.







                                                               26











                       Leaking fixtures


                              This is one of the most common causes or contributors to drainfield failure.
                       Repair or replacement of the offending fixture or fixtures is the first step in
                       correcting the problem. Homeowner education is essential because it is the only
                       way to assure that the problem does not reoccur. Fixtures that fail once and are
                       repaired will fail again in time. Therefore, take time to explain to the homeowner
                       what to look for and how to test for leaking toilets. Discuss the cost of repairing a
                       drainfield versus the cost repairing fixtures occasionally. Don't rush the
                       discussion; take your time to make your point clearly and in a friendly manner.


                       Surface water and miscellaneous other sources,


                              Surface water includes run-off from roofs, footer drains, basement sump
                       pumps, driveways, patios, undeveloped upslope areas. Other miscellaneous sources
                       may include discharges from water softeners, swimming pools, hot tubs, lawn
                       irrigation systems and other uses. None of this water should be directed into or on
                       top of a drainfield. Where problems such as this are encountered, the water should
                       be diverted to another area or piped beyond the drainfield area before being
                       discharged.


                              The improper management of surface water and other extraneous water is a
                       major leading cause of failure. The importance of controlling surface water should
                       not be underestimated when evaluating a failure. Permits for repairs should
                       incorporate explicit information on controlling surface water.



                       Addressing physical causes of failure


                       Broken, blocked or damaged comi3onents


                              Repair in this instance normally requires replacing broken or damaged
                       parts or removing any blockage in the system. It is important to determine if the
                       situation is an isolated or a reoccurring problem. Occasionally changes in
                       landscaping (such as extensive regrading or relocation of a driveway) can create a
                       problem that needs to be corrected to prevent the problem from reoccurring. This
                       is very different from damage occurring from isolated or nonroutine events which
                       will not cause continuing difficulties.


                                                                27












                         Tree roots


                                 The obvious solution is to remove the offending tree roots and reseal the
                         points of entry to prevent infiltration, exfiltration and the re-entry of new roots.
                         Removal of the offending tree is normally, if not always, necessary. There is
                         anecdotal evidence that treatment of the system with copper sulfate will at least
                         temporarily provide relief from root blockages. At this time there is no practical
                         data indicating what the long term effects of such treatment are on groundwater or
                         nearby vegetation. Further, proper dosages have not been documented to achieve
                         the desired resUltSwithout adverse impacts. Consequently, at this time the
                         Department does not recommend the use of copper sulfate (or other compounds) for
                         controlling unwanted root penetration into onsite systems.


                         Improper venting


                                 Venting is done to allow air to freely enter the plumbing system. When a
                         plumbing system is not properly vented, pressures less than that of the atmosphere
                         may occur within a pipe or pipes. This can result in sluggish drains or complete
                         backups. Improper venting is a problem that is rarely encountered in new
                         construction due to adequate plumbing code provisions. Occasionally, older
                         systems (>30 years typically) will have a venting problem. These problems are
                         generally typified by sluggish plumbing and apparent intermittent blockages.
                         Normally the drains are the first suspect. When no problem is discovered in the
                         drainage system the vent system should be inspected and/or snaked out. In either
                         new or old systems, a vent can be blocked by a birds nest or a dead animal
                         (squirrels seeking innovative housing are prime offenders). In addition, vents
                         branching off of the horizontal part of the sewer drain may fail to function properly
                         in areas with a high seasonal water table. The vent should be located off of the
                         vertical portion of the sewer line.



                         Addressing problems with landscape position


                         Systems in a concave position


                                 When a drainfield is has been installed in a poor landscape position, little
                         can be done to correct the problem short of relocating the system. Relocating the



                                                                    28










                         system should be the prime objective whenever this situation is encountered.
                         When sites on the owners property are limited, easements should be considered.


                                When relocating a system is not possible, the only remaining option is to
                         manage the failure to minimize the amount of effluent surfacing. A french drain
                         uphill, and if appropriate on one or both sides of the system should be installed. A
                         french drain is nothing more than a gravel filled trench designed to intercept water
                         and pipe it to another location. Typically, they are constructed like a drainfield
                         (occasionally with more gravel) and have the perforated pipe located at, the bottom
                         of the trench rather than the top. The preferred material is not three hole
                         drainfield pipe, but rather slotted pipe like that used in footer drains. If drainfield
                         pipe is used, placement of the holes either up or down is not significant (aside from
                         lunch time debates).


                                The french drain should be anchored to a restrictive layer if one exists (i.e.,
                         installed so that the french drain trench bottom rests on or in the restriction). If
                         no restriction exists, the drain should be installed at the same depth as the
                         drainfield. The french drain should be installed 20 feet away from the absorption
                         field if possible. Under no circumstance should the drain be installed any closer
                         than ten feet to the drainfield. The french drain is not a cure all solution. It will
                         help in most problem landscape positions but it will not cure the problem and
                         should not be presented as such.


                                The area over the french drain should be graded to divert surface run-off
                         into the drain and away from the drainfield. When possible, the drainfield area
                         should be capped and crowned to improve run-off and reduce infiltration of any
                         precipitation falling on the site. Surface water should be managed as described
                         below. Water saving fixtures should be installed in the dwelling and the
                         homeowner instructed on water conservation measures.




                         Addressing soil related problems


                         Water table


                                In this instance the reference to a water table means the presence of a
                         water table at a distance less than the minimum required stand-off established by
                         regulation. The primary difficulty in this situation in the coastal zone area is


                                                                   29










                       inadequate treatment capacity within the soil. Wastewater disposal is a problem
                       but is frequently secondary in nature. Solutions to shallow depths to a water table
                       include installing an enhanced flow system shallow (12 to 18 inches), a LPD
                       system as shallow as 12 inches, the use of drip disposal installed shallow (12 to 18
                       inches), elevated sand mounds and pretreatment. The selection of a methodology
                       depends upon the severity of the problem.


                              When at least 12 inches of stand-off can be maintained by installing a
                       system between 12 and 18 inches from the ground surface, then either low
                       pressure or drip disposal, alone or with pretreatment, is an appropriate solution.
                       When a water table occurs between 18 and 24 inches in a highly permeable (<30
                       mpi) soil, an elevated sand mound is an appropriate solution to provide treatment
                       and disposal.


                              When the water table is located within 18 inches of the ground surface,
                       pretreatment must be considered. Either a recirculating sand filter or a lined
                       intermittent sand filter will improve the level of treatment. The method of
                       disposal should be selected to utilize as much aerobic soil treatment as possible.
                       Consideration should be given to the method most likely to provide reliable
                       disposal. Hence, enhanced flow, LPD or drip disposal should be seriously
                       considered. Whenever possible, set-back distances to wells, shellfish water, lakes,
                       ponds and streams should be increased beyond the minimum to allow for reduced
                       soil treatment efficiency. One hundred feet or more to surface water should be
                       practiced where ever lot size allows.


                       Slow percolation rates


                              Soils with slow percolation rates as their only problem are few and far
                       between. Normally, soils with slow rates have another problem, such as a
                       restrictive layer or plastic properties that contribute to, or are causing the slow
                       rate problem. The primary solution to soils with rate problems are increasing the
                       drainfield size and improving effluent distribution. Hence, either LPD or drip
                       disposal will enhance the effectiveness of a repair. They also respond very well to
                       water use management and reduction.


                              The specialist considering a repair in soils with slow percolation rates
                       should evaluate the history of water use in the dwelling. Has there been any
                       recent change due to new occupants, growing family etc., with a resultant change


                                                               30










                        in how much water has been used? How long the system has been operating
                        satisfactorily under the present water usage? This information can assist in sizing
                        a new field. By comparing the soil and water use estimates between the old
                        drainfield and the new site, an attempt can be made to design a system with a 15
                        to 25 year life expectancy. Such a design should include permanent water saving
                        fixtures and at least enhanced flow distribution. Low pressure distribution and
                        drip disposal are options that are especially well suited to slow rate soils.


                        Plastic clays


                               Plastic clay soils have no onsite wastewater disposal solutions. This is a
                        situation where failures are managed not repaired. Strict water conservation will
                        help more than any other solution. Pump and haul is an expensive option that a
                        few may find satisfactory. Separating gray water from black water and pumping
                        and hauling the black water, while putting the gray water into a drainfield may
                        reduce these costs will also reducing health risks associated with a failing
                        drainfield. Repairs attempted in plastic soils should generally be made shallow, in
                        the least plastic horizon, and maximize the effects of evapotransporation.
                        Additionally, homeowners should be advised that the probability of successfully
                        repairing such a system is low. Every effort should be made toward managing the
                        problem as correction is not a likely outcome.


                        Soil cloggin


                               Soil clogging, organic mat formation, or creeping failure are all evidence of
                        an old system, an undersized system, or both. If sufficient area is available, these
                        systems are usually easy, albeit expensive to repair. Drainfield replacement in the
                        normal solution. Where soil clogging is the only problem, the specialist should
                        evaluate the size and condition of the septic tank and tees before considering their
                        reuse. The age of the system and the patterns of water use (as discussed under
                        slow rates should also be considered and compared to the new site when designing
                        a repair.


                               Whenever possible, repairs to a clogged system should be in a manner that
                        preserves the original system. Given 5ufficient time to rest, most of these failed
                        systems will recover sufficiently to be usable, to some degree, in the future.
                        Installation of a flow diversion valve and the installation of a new system (and
                        probable expansion of the old system) are suggested.


                                                                 31










                               When sufficient area is not available to replace a system, a repair can be
                        made by "going between" the existing laterals. Prior to attempting a repair, the
                        system should be allowed to rest for as long as possible. This will help prevent soil
                        smearing and make for better (but not necessarily pleasant) working conditions
                        when installing the system.


                               It is rarely possible to repair a system "between the laterals" without
                        encountering portions of the old system. Therefore consideration of alternating
                        between the old and new systems probably will not be possible. If the soils are
                        sufficiently deep, it is recommended that when repairing between laterals, that the
                        repair be installed deeper than the original system. This will tend to avoid areas
                        in the soil where the original system has caused soil clogging and chemical
                        reduction of the soil (evidenced by gleying and organic staining) and potentially
                        reduced infiltration rates (Allison, 1947 and Daniel and Bouma, 1974). Even six to
                        twelve inches additional depth will provide some benefit in this respect.


                        Restrictive horizons


                               The variety of pans, discontinuities, impervious layers and restrictions
                        sometimes seems infinite and at odds with successful treatment and disposal
                        objectives. Overcoming the limits of soil restrictions takes outstanding skills if one
                        is to be consistently successful.


                               The best way to visualize a restriction is not as an impervious layer but
                        rather as a soil horizon with severely restricted water flow through the boundary.
                        When a satisfactory horizon below the restriction exists, the solution to the
                        problem is easy. Install the drainfield below the restriction and anchor a french
                        drain to the restriction above the drainfield. Unfortunately, most problems are not
                        so simple.


                               When no satisfactory horizon exists below the restriction, the specialist
                        should design a system that minimizes the actual loading rate applied to the
                        restrictive layer (as opposed to the trench bottom). This is achieved by
                        maintaining the greatest possible separation distance between the trench bottom
                        and the drainfield, reducing the loading rate applied to the trench bottoms (i.e.,
                        over-sizing the system to accommodate for reduced permeability of the restriction),
                        using drip disposal or LPD and potentially modifying trench spacing.



                                                                  32










                               Consider the effluent leaving the trenches. As it moves into the soil it
                       spreads out and is affected by gravity. On all sites the effluent tends to move
                       downward and outward. On sloping sites the downward component of movement
                       includes a downslope vector. The objective when designing a repair for these soils
                       is to allow the effluent to move outward sufficiently, so that when it encounters the
                       restrictions, the effluent application rate does not exceed the permeability of the
                       restriction.


                              On sloping sites, the downslope component of movement will cause the soil
                       beneath each successive lower lateral to have higher loading rate than the laterals
                       upslope. To counter act this effect, the separation distance between laterals may
                       be increased forthe lower laterals. This reduces the application rate to the
                       restrictive horizon and helps reduce the chance of a failure in one of the lower
                       laterals due to what essentially amounts to water mounding.
































                                                                33








                                                          Chapter 5


                                                 Component Functions


                                         Pretreatment Methods and Appurtenances


                       Septic Tank


                       Description


                              The septic tank functions to remove large solid particles from the effluent
                       before it passes to the absorption field. This is accomplished by physical settling of
                       solids, floating of grease and through anaerobic decomposition. In order for these
                       processes to occur efficiently, several conditions must be met.


                              The tank must be of sufficient size and appropriately shaped to allow
                       settling to occur. Typically length to width ratios are nominally 2:1 and width to
                       depth ratios are nominally 1:1. The Sewage Handling and Disposal Regulations
                       allow for nominal length to width ratios ranging from 2:1 to 3:1 and width to depth
                       ratios of 1:1.


                              Tanks are normally constructed out of 3,000 psi concrete with either
                       reinforcing wire or synthetic fiber. The material the tank is constructed of from is
                       important only insofar as it is resistant to the corrosive action of the wastewater,
                       that it be watertight, that it is strong enough to support bearing loads placed on it,
                       and that it will not "float" under adverse high water table conditions.


                              Decomposition in the septic tank, of the organic material present in the
                       wastewater, is a natural process. Decomposing bacteria are introduced to the
                       system through normal use. Therefore the use of additives is not recommended.
                       Additives can be detrimental and have not been shown to be beneficial to the long
                       term process of settling and decomposition.


                       Application


                              The septic tank is the most common method of providing pretreatment in
                       onsite wastewater disposal practice. The method is simple, low in cost, requires


                                                               34









                        minimal maintenance and is somewhat effective at keeping solids out of the
                        absorption area.


                                In order for efficient anaerobic decomposition to occur bacteria must have a
                        favorable environment and a food source. This is not typically how most of us
                        envision conditions inside a septic tank. Fortunately, there are organisms that
                        thrive on wastewater constituents and find the septic tank a hospitable
                        environment. These organisms, which are generally not disease causing, consume
                        and compete with other harmful organisms found in the wastewater. They also
                        convert most of the solid materials to carbon dioxide, water and methane gas.
                        Because they are not 100% efficient, solids accumulate in the bottom of the tank
                        and must be removed periodically.


                                Failure to pump a tank out frequently enough can permit solids to pass to
                        the drainf ield where they will clog soil pores. Eventually this will lead to a failure
                        of the system. The frequency that a given tank will need to be pumped will vary
                        with use. The size of the tank, the organic loading rate, the hydraulic loading rate,
                        and use of chemicals that reduce biological activity will all affect the frequency
                        withwhich a tank will need to be pumped.

                                Most of these conditions are beyond practical control 'after a system has
                        been permitted; hence proper septic tank sizing and design is important. The
                        organic loading rate will be determined by the number of people using the system
                        and the presence or absence of a garbage disposal. When a garbage disposal is
                        present, relatively large amounts of cellulose will be added to the system.
                        Cellulose is fairly resistant to decomposition in the septic tank and will result in
                        the accelerated accumulation of solids in the tank. Generally, under "average use"
                        a septic tank should be pumped every three to five years. When a garbage disposal
                        is used, the tank should be pumped annually.


                                The only readily controllable aspects affecting the environment in a tank
                        after it has been installed are what is added to the tank. Organic constituents
                        have been discussed and are not readily controllable. The hydraulic loading rate
                        and the addition of chemicals, harmful to the organisms in the tank, can be
                        controlled to some degree through the use of flow reduction devices and owner
                        awareness. The use of laundry detergents, bleach and household cleaners in
                        finormal" amounts is usually not a problem. The use of excessive amounts of these
                        compounds, or of water flow in excess of design capacity can cause problems.


                                                                   35











                        Advantages


                               The septic tank, as previously noted is a passive design, low in initial cost
                        and in maintenance.


                        Disadvantages


                               The septic tank is rarely considered more than 60% effective at reducing
                        solids in the waste flow. There is essentially no reduction in BOD or fecal
                        coliforms.



                        I)ual septic tanks and multiple compartment tanks


                               The disadvantages and application of dual septic tanks are essentially
                        identical to a single tank. Costs are approximately doubled over a single tank
                        installation but efficiency is increased. In short, the longer the retention time for
                        settling the better. Multi compartment septic tanks are require less excavation
                        and may be less expensive than dual tanks. Multi compartment tanks are at least
                        as effective at removing solids as dual tanks.


                               The installation of two septic tanks in series (or multi compartment tanks)
                        has been used as a strategy to reduce the amount of suspended solids which reach
                        the drainfield. The first tank provides the major portion of 'the settling and the
                        second tank gives additional settling time for the remaining lighter solids which
                        did not settle out in the first tank. Dual tanks provide protection against
                        turbulence and surges which may cause solids to move out into the drainfield. If
                        the hydraulic loading of the systern has exceeded the ability of the septic tank to
                        provide an adequate retention time a second tank in series should be added. The
                        first tank must provide a minimum storage volume greater than 50% of the daily
                        water flow.















                                                                  36











                       Sand Filters


                       Description


                              Sand filters may be broken down into three different types of designs;
                       gravity flow or trickling sand filters, intermittent or dosed sand filters and
                       recirculating sand filters. All three are capable of giving good to excellent
                       treatment with each having its own unique advantages and disadvantages.
                       Trickling sand filters are the simplest design, relying on gravity flow to apply
                       effluent. They are also generally the largest in size and the design most subject to
                       problems with channelized flow. Intermittent sand filters rely on pumps or
                       siphons to do5e the septic tank effluent onto the filter. They are substantially
                       smaller in size than gravity flow sand filters and are generally considered to be
                       very reliable in terms of effluent quality. The reduced size is a function of an
                       increased hydraulic loading rate which is made possible because effluent is applied
                       more efficiently to the filter. Recirculating sand filters are the most compact
                       design of the three. Again the size reduction is a function of loadings which are
                       higher for recirculating sand filters than either of the other two designs. A portion
                       of the filtered effluent is returned back to the pump chamber to be recycled
                       through the sand filter again. Properly designed and sized, recirculating sand
                       filters can"yield excellent treatment results.


                       Application


                              The primary, if not exclusive, function of a sand filter applied to repair a
                       failing onsite system is to provide additional effluent treatment. This objective
                       should always be considered when soil properties do not lend then-Lselve5 to
                       providing adequate treatment.


                       Advantages


                              EMuent from the sand filter, without disinfection, will show a reduction in
                       coliform. organisms of from 3 to 4 logs and BOD and suspended solid reductions
                       down to 30 mg/l each or less.







                                                                37










                        Disadvantages


                                About, the only disadvantage to adding a sand filter to a system is the
                        increase in cost and complexity. Most sand filter systems require a pump which
                        adds to the cost and reduces consumer acceptance of the system.



                        Aerobic Pretreatment


                        Description


                                Aerobic pretreatment in this context is used to refer to mechanical aeration
                        of effluent by an aerobic treatment unit (ATU). Aerobically treated effluent has
                        been proposed to rejuvenate drainfields which have failed due to organic clogging.
                        They have also been proposed as a method of pretreating effluent to reduce BOD
                        and improve the disposal capacity of the soil and as a means to reduce the odor
                        and nuisance associated with a failing system.


                        Application


                                Little or no published literature exists to support these potential benefits.





                        Constructed Wetlands


                        Description


                                Constructed wetlands, as used in the context of this manual, are shallow,
                        gravel filled beds, planted with wetland species, which are designed to treat
                        effluent. They are a developing technology and much is yet to be learned about
                        their operation, effectiveness and appropriate application.


                                Two major design philosophies exist at this time. A pioneer in the
                        constructed wetland concept is B. C. Wolverton, Ph.D. He proposed a design which
                        consisted of one or more, long narrow trencher, 18 to 24 inches deep, planted with
                        Calla lilies or other species. Effluent quality was excellent with reported BOD and
                        SS values often well below 10 mg/l. The design was adapted by local


                                                                   38










                       environmental health specialists in Mississippi (where Wolverton did his research)
                       and subsequently spread to other states.


                              The Tennessee Valley Authority (TVA) published a report (see appendix)
                       describing a modification of the Wolverton design. The TVA design uses shorter,
                       wider beds to reduce the likelihood of clogging by organic matter. Preliminary data
                       indicate that these systems are less likely to clog than the Wolverton design but do
                       not produce the effluent quality that can be expected from the NASA design. It
                       appears to be a classic case of trade-offs. One can have high quality effluent and
                       reduced reliability or vice-versa. Alternatively, the two design concepts may be
                       able to be merged achieving both reliability and treatment efficiency. But not
                       without a new trade-off-, cost. Combining designs appears to increase the system
                       cost in proportion to the complexity of the design.


                       Application


                              Constructed wetlands (CW) are a developing technology which may have
                       potential to provide pretreatment in soils where adequate disposal capacity exists
                       but treatment capacities are low. Situations where a failing system is located in
                       permeable soils with a high water table, this system may have potential to provide
                       adequate pretreatment to make a repair feasible.


                       Advantages


                              The primary advantage of the wetland design is its passive treatment
                       concept. Except for harvesting plants annually, there is little user maintenance.
                       Treatment occurs in the system without mechanical parts to break down and
                       without user input. The system also appeals to environmentally sensitive
                       individuals as a design that is inherently in concert with nature.


                       Disadvantages


                              As with any developing technology, many design and performance
                       parameters are unknown. The life expectancy, long term maintenance
                       requirements. and long term performance are all unknown at this time.






                                                                39












                         Tees


                         Description


                                 Each septic tank should be fitted with both inlet and outlet tees. Tees today
                         are typically schedule 40 PVC or cast in place with the septic tank. Older tees
                         were often cast iron, a material with a limited life expectancy in a septic tank.
                         The tees have four purposes. They reduce the amount of floating solids leaving the
                         septic tank; they vent gasses back through the house plumbing to the vent(s)
                         located of the roof of the house, the help maintain the quiescent nature of the tank
                         by baffling flow into the tank and they create grease holding capacity within the
                         tank.


                                 The tee on the inlet side generally extends into the septic tank effluent to a
                         depth of one foot while the outlet tee generally extends to a depth of one-third the
                         liquid depth (nominally 18 inches) of the tank. Both tees extend eight to ten
                         inches above the liquid level in the tank to provide grease holding capacity.



                         Zabel filter


                                 The Zabel Multi-Purpose Filter is a commercially available product on the
                         market designed to reduce the amount of solids which will leave the septic tank.
                         The manufacturer claims at least a 67% reduction over other methods of retaining
                         solids. The filter is placed in the septic tank where an outlet tee would normally
                         be installed. Over a period of time the filter will need cleaning. This can be
                         accomplished by rinsing it with high pressure water (a garden hose with a spray
                         nozzle).


                                 The filter may help protect LPD's from orifice plugging due to hair and
                         other suspended solids. Research has shown that most BOD from a septic tank is
                         dissolved so a mechanical filter will not reduce organic loading. The soil must
                         therefore treat the same amount of water and waste load.











                                                                     40










                        Vent Pipe


                        Description


                               The vent pipe (or Pipes) is part of the plumbing system. It is designed to
                        assure that normal atmospheric pressure is maintained throughout the system of
                        drain pipes in the house. Without proper venting, under some circumstances, a
                        vacuum would be created which would completely stop the flow of water through
                        the drain. Noxious gasses, mostly from the septic tank and sewer line, are also
                        vented up to the roof where they are released.


                               Odors from the vent system are rarely (but not never) a problem. When
                        they are a problem there are several possible solutions. On newer septic systems
                        (less than 3 years old and often less than a year) which are significantly under-
                        loaded objectionable odors may occur. Odors may also occur when atmospheric
                        conditions are such that the vent gasses settle to the ground near the stack instead
                        of blowing away. This is typically a short term condition and requires no remedy.






                                                 Final Treatment and Disposal
                                                  Methods and Appurtenances



                        Drainfleld


                        Description


                               The drainfield is the single most important element in the wastewater
                        system. While the other elements can be manipulated in the design and planning
                        phases to match the user's needs, man cannot effectively alter the quality of the
                        soil on the site. Even after a system is installed, other components can be modified
                        or replaced. The soil, where most of the eMuent treatment and disposal actually
                        occurs, cannot be altered. Systems must be designed to utilize the best soil
                        properties and accommodate for the worst soil properties; otherwise another failure
                        is inevitable.





                                                                 41










                               The drainfield is composed of a series of trenches, installed on contour, up
                        to 100 feet long and usually 2 or 3 feet wide. The trench depth is determined
                        based on soil permeability, depth to restrictive horizons and depth to other
                        treatment limiting factors such as rock or water table. The trench normally has 13
                        inches of stone installed with a 4 inch perforated pipe running the length of the
                        trench nominally 1 to 2 inches below the top of the gravel.


                               Effluent leaves the pipe near the beginning of the trench, enters the gravel
                        and follows the trench bottom until it is absorbed into the soil. A biologically
                        active zone is created at the interface between the gravel and the soil. This zone,
                        often referred to as an organic (and less often as a zoogleal mat), acts as both a
                        biological filter and a restrictive layer.


                        Application


                               The ideal drainfield application is to sites where 2 to 4 feet of unsaturated
                        soil exists below the trench bottom to complete the process of renovating the
                        effluent. In reality this is rarely the case with new construction and is even less
                        likely to occur in repair situations, In practice, 18 inches (or more) of unsaturated
                        soil should be present for treatment. In many repair situations there will be
                        significantly less than 18 inches Of suitable soil with which to work. When this
                        stand-off distance cannot be met, a drainfield can also be used in concert with
                        other technologies, such as various pretreatment schemes or shallow placement
                        methods in order to achieve equivalent treatment.


                        Advantages


                               The drainfield is by far the most common method of wastewater treatment
                        and disposal. It is cost effective, environmentally safe when proper site conditions
                        are met, and contractors abound who can competently install this type of system.


                        Disadvantages


                               Many sites are inappropriate for a conventional drainfield. Water table,
                        rock, restrictive horizons or other limiting factors may preclude a drainfield from
                        both treating and disposing of sewage. This can result in wells becoming
                        contaminated or sewage surfacing on top of the ground.



                                                                  42










                       Dosed systems conventional (enhanced now)


                       Description


                             Enhanced flow technology is nothing more than a conventional septic tank
                       and drainfield system, sized and sited according to current regulations, that has
                       effluent applied in a manner designed distribute effluent more evenly between
                       laterals. The only additional appurtenance is a conventional pump chamber with a
                       float control system and an audio visual alarm. The pump and pump chamber, in
                       some instances, may be somewhat larger than a conventional pump chamber used
                       only to overcome gravity.


                       Application


                             Dosed systems are most appropriate where the intermittent application of
                       effluent will assist in either the treatment or disposal of effluent. Soils with slow
                       percolation rates will benefit the most.


                       Advantages


                             Enhanced flow is a simple technology offering modest gains in optimizing
                       effluent distribution. Contractom are familiar with construction techniques and
                       homeowner acceptance should not present problems. Where cost is a factor, a
                       shallow placed, enhanced flow system may provide an acceptable compromise when
                       compared to LPD.


                       Disadvantages


                             Aside from the additional cost of a pump and the modest reduction in
                       system reliability v.s. systems without a pump, enhance flow systems have no
                       significant disadvantages.











                                                              43












                         Low Pressure Distribution


                         Description


                                Low pressure distribution (LPD) systems are essentially just a modified
                         drainfield. Effluent is conveyed to the absorption area of an LPD system by pump
                         rather than gravity. The absorption trenches have 1.25 to 1.5 inch PVC pipe with
                         small diameter holes (3/16" to 1/4"). The effluent from the pump pressurizes a
                         manifold that distributes the effluent evenly throughout the piping in the laterals.



                                By design, the LPD system is intended to provide nearly equal amounts of
                         effluent to each lateral as well as assuring that the entire length of each lateral is
                         used. In contrast, a conventional gravity flow drainfield typically has 30% to 50%
                         flow variation between laterals when installed and has no provision for distributing
                         effluent evenly along the trench length. LpD systems are designed to eliminate
                         ponding along the trench bottom. This provides for aerobic conditions in the trench
                         to maximize the rate of treatment of the effluent. Where sustained ponding occurs,
                         the system is undersized.


                         Application


                                Low pressure distribution systems lend themselves to truly marginal soils.
                         These are soils that are not deep enough in terms of depth to rock or water table
                         for a conventional system or are just barely deep enough but for one reason or
                         another require special precautions. Soils with slower than average percolation
                         rates can also be used successfully. Under no circumstances should LPD
                         technology be applied where plastic soils are encountered. The even distribution of
                         effluent wets the soil causing swelling and effluent ponding begins almost
                         immediately.



                         Advantages


                                LPD systems offer the ability to make installations as shallow as 12 inches
                         and thereby maintain or increase separation distances to limiting soil features.
                         Experimentally, LPD has been installed at original surface grade successfully.
                         Gravel "trenches" are built on a plowed surface, the laterals and manifold are


                                                                   44









                       installed and the system covered deep enough to prevent freezing or physical
                       damage. The cost of LPD systems is moderate but generally not considered
                       excessive. Additionally, because of their theoretical longevity, (due to dosing and
                       even distribution) they may prove to be a better value (cost per unit time) than
                       most systems.


                       Disadvantages


                              The primary disadvantages of LPD systems are the increased cost compared
                       to a conventional system, the potential for pump failure and plugging of the
                       laterals and throttling valves. LPD systems require routine maintenance after the
                       first three to five years.


                              LPD's must be designed for each specific site by a qualified designer. No
                       two systems are alike. Proper placement, controls and pump selection are critical.
                       Pump replacement in the future is also critical to make sure the System operates
                       as designed.



                       Elevated Sand mounds


                       Description


                              Elevated sand mounds (ESM) dispose of septic tank effluent by applying it
                       to a sand bed built over natural soil. The sand media provides effluent treatment
                       prior to its disposal into the natural soil for final treatment and disposal.



                       Application


                              Elevated sand mounds are most appropriate where disposal issues are not a
                       concern but the existing soils are not capable of providing adequate treatment
                       before allowing the effluent to enter the groundwater or fractured rock. Ideally,
                       the combination of sand in the mound (12 to 24 inches) plus the underlying
                       suitable soil (18 to 60 inches, or more) will provide for satisfactory effluent
                       renovation. In all repair situations this should be the goal. Unfortunately this
                       goal cannot always be realized.




                                                               45











                        Advantages


                               The primary advantages of the ESM is its ability to treat and dispose of
                        septic tank effluent in a small area. Mounds are not however, a panacea for all
                        sites that are unsuited for drainfields.


                        Disadvantages


                               The primary disadvantage of a mound is the cost. The expense varies with
                        locality but $7,000 to $10,000 cost estimates are commonly cited. Additionally,
                        another less significant disadvantage is that the ESM utilizes a pump. Pumps will
                        eventually need to be replaced and are considered as a disadvantage by some
                        individuals.


                               Additionally, improperly sited mounds frequently leak at the base of the
                        mound. Most drainfield failures occur on sites that are not particularly well suited
                        for a mound. The. specialist should use caution when establishing a repair strategy
                        using a mound on a poorly suited site. At a minimum the homeowner should be
                        aware of the costs and potential for leakage. The specialist should also document
                        that the expected result will be an improvement over the existing conditions.
                        Frequently the wastewater from a leaking mound is low in fecal organisms and
                        may well represent an improvement over a failing drainfield. Simply put, don't
                        consider the mound as a panacea and do not over sell it on marginally suited sites.
                        On sites meeting the criteria for siting a mound, they are an effective and
                        appropriate repair methodology.



                        Drip disposal or "trickle" irrigation


                        Description


                               Trickle irrigation is a developing technology, based on using flexible
                        irrigation tubing to dispose of effluent. The tubing used is flexible plastic pipe
                        with emitters installed at set intervals. The emitters drip at a fairly constant
                        interval over a wide range of pressurery. Unlike LPD design, pressure variation is
                        Usually of no concern. Some manufacturers have been installing drip systems for
                        over five years. It has been successfully used for a number of years in agriculture.



                                                                46









                              These systems are basically designed to be high pressure distribution fluid
                       handling systems. The effluent pumped into the drip tubes must be free of solids
                       to avoid clogging the emitters. At least two different pretreatment schemes have
                       been developed to accomplish this. Several manufacturers use aerobic
                       pretreatment to remove solids. Another manufacturer is filtering septic tank
                       effluent through a proprietary disk filter. Much like LPD's, these systems need to
                       be designed for each specific site.


                       Application


                              This technology may be applicable in the same situations where a LPD
                       would be appropriate.


                       Advantages


                              The cost of operating a tri ckle irrigation system are not yet known.
                       Methods of installing the pipe vary and can involve the use of a conventional
                       backhoe or in some instances use a chisel plow. In the latter instance, site
                       disturbance is minimal compared to a backhoe.


                       Disadvantages


                              Mostly unknown at this time. Where ATUs are employed, maintenance
                       similar to that required by the Discharging Regulations must be employed. The
                       cost of materials (w/o an ATU) has been given as approximately $3,000 by one
                       company. It appears then that this technology will be competitive with LPD
                       systems.





                       Distribution Box


                       Description


                              The distribution box has a single purpose: to divide effluent flows evenly
                       among absorption field laterals. Unfortunately, the distribution box is not an
                       efficient or effective method of achieving equal flow splitting.



                                                               47









                                 Ideally the distribution box should be placed on a concrete pad or otherwise
                          solidly anchored to prevent it from tilting or shifting in place. The use of Speed
                          Levelers' or Dial-a-Flows' facilitates future adjustments. Because of their
                          constant radius and ease of adjustment, these devices most likely improve the
                          accuracy with which a box can be leveled initially and in the future.


                          Application


                                 The distribution box may be used anywhere effluent is to be split between
                          multiple laterals and even distribution is not critical. Most new drainficilds fall
                          into this category where the soils are clearly satisfactory. When repairing a failing
                          system better than average distribution may be necessary to assure that no portion
                          of the soil absorption system is overloaded.


                          Advantages


                                 The primary advantages of the distribution box are its low cost, ease of
                          installation, and contractor familiarity.


                          Disadvantages


                                 The distribution box is unquestionably the weak link in any gravity flow
                          system. Minor shifts in elevation will alter flow patterns in a gravity flow
                          distribution box significantly. The most serious problems occur when a
                          distribution box is tilted to allow excess flow to the lowest lateral.


                          Flow diversion valves


                          Description


                                 A flow diversion valve is a device installed in the effluent line between the
                          septic tank 'and the distribution box. It requires the use of two absorption fields,
                          each normally equal to half the required absorption field area. When dealing with
                          repairs in marginal and unsuitable soils, larger absorption areas may be
                          appropriate. The flow diversion valve is a manually operated device that directs
                          flow exclusively to one absorption field. Periodically (usually annually) the valve is
                          switched and the second field is placed into use while the first one is allowed to
                          rest.



                                                                    48











                     Application


                            Flow diversion valves do not achieve unsaturated flow like LPD or drip
                     disposal but it does provide a mechanism to allow for long term wetting and drying
                     periods. When there is adequate area to replace a drainfield entirely and the soils
                     are not entirely satisfactory, a flow diversion valve may be installed to allow the
                     homeowner to alternate between the old and the new systems. At least one year,
                     and preferably several years should be allowed to pass before reusing the old
                     system.


                            When a failing system is repaired "between the lines" there is often an urge
                     to use a flow diversion valve. If this is to be done, extreme care must be taken
                     during installation of the repair to assure that the old system is not intersected. If
                     this occurs, it will not be possible to maintain hydraulic separation of the two
                     systems and using a flow diversion valve will accomplish little or nothing.
                     Realistically, installing a 3 foot wide trench between two other 3 foot wide
                     trenches, 9 feet on center without knowing the precise location of the original
                     trenches will be impossible.


                     Advantages


                            Flow diversion allows for long term periods of wetting and drying which
                     allows soils to renew their absorptive capacity. While apparently not as effective
                     as LPD or drip disposal, the concept is very inexpensive to apply. Materials are
                     readily available and competent installation is widely available.


                            Long term resting has been proven to be the only way to rejuvenate a
                     drainfield. Resting can at least partially reverse damage due to both organic
                     overload and hydraulic overload.


                            Diversion valves can be successfully used on slower soils to rejuvenate each
                     half on an annual basis. Plus, in the event of failure, a standby system is already
                     in place. A properly sized and installed gravity system will easily last several
                     years on 1/2 of the design. Providing long term resting for gravity systems is the
                     best available strategy for making conventional systems a permanent solution to
                     onsite wastewater treatment and disposal.





                                                            49











                       Disadvantages


                              The only practical disadvantage of using a flow diversion valve is assuring
                       that they are routinely switched to allow both fields to be used.



                                                   Privies and Blackwater
                                                      Treatment Devices




                       Composting toilets


                       Description


                              Composting toilets compost human waste (along with additional
                       carbonaceous matter that may be needed) and produce a humus like material after
                       six months to a year of biological action. The resulting material, when properly
                       composted, should be safe to dispose of by burying it. This should never be done in
                       vegetable garden. fn actuality, new fecal matter is continually added to. the
                       composting pile and whatever material is removed should be treated as if it is
                       contaminated with fresh feces.


                       Application


                              Composting toilets can be used to treat human black water under the
                       Sewage Handling and Disposal Regulations The two best advantages of the
                       method are where there is little or no grey water being produced (i.e*., certain
                       commercial or recreational uses) and where conditions exist that make it necessary
                       to separate the black and grey water components out and treat them separately.
                       Generally the C:N ration should be approximately 25:1. Consequently it is
                       frequently necessary to add carbon to make up for excess nitrogen. Shredded
                       newspaper or kitchen garbage (also shredded) can be used to balance the C:N ratio.


                       Advantages


                              The primary advantage of composting toilets is that their use and
                       functioning are entirely independent of site and soil conditions.

   is                                                          50











                       Disadvantages


                              Disadvantages to the systems are public acceptance, cost, difficulty
                       installing in existing structures, odors and problems maintaining a carbon to
                       nitrogen ratio (C:N) suitable for good composting action. Composting toilets are
                       expensive when one considers that they represent only a portion of the wastewater
                       disposal solution. In some instances they have been reported to cause
                       o@jectionable odor problems. Mechanical ventilation kits for these systems can
                       reduce or eliminate this complaint. Installation is difficult or impossible for
                       existing construction and the compo5ting chamber, which resides one floor below
                       the toilet, requires substantial space. Either a basement is needed (for one story
                       homes) or first floor space must be given up when the toilet is installed on a second
                       floor. Finally, many individuals find it difficult adjusting to having an indoor
                       privy. Not flushing and having to feed the system a carbon source amounts to a
                       lifestyle adjustment that is difficult to make.



                       Vault privies


                              Vault privies are privies built over a septic tank or other type of vault.
                       Their purpose and applications are similar to those of a composting toilet but are
                       most useful where an outdoor privy is acceptable. Vault privies are periodically
                       pumped out to remove accumulated organic matter.





















                                                               51














                                                            References



                        Allison, L.E. 1947. Effect of microorganisms on permeability of soil under
                        prolonged submergence. Soil Sci. 63: 439-450


                        Avnimelech, Y. and Z. Nevo, 1964. Biological clogging of sands. Soil Sci. 98:222-
                        226.


                        Baum, S.J. 1982. Introduction to organic and biological chemistry. Macmillian
                        Publishing Co., Inc., New York.


                        Daniel, T.C. and J. Bouma. 1974. Column studies of soil clogging in a slowly
                        permeable soil as a function of effluent quality. J. Environ. Qual. 3: 231-326.


                        Kristiansen, R. 1982. The soil as a renovating medium. The fate of pollutants in
                        soil-organic material. In A.S., and R.W. Seabloom (eds.) Alternative Wastewater
                        Treatment. D. Reidel Publ. pp. 121-128.


                        Reneau, R.B., Jr., and D.E. Petry. 1975. Movement of coliform. bacteria from septic
                        tank effluent through selected coastal plain soils of Virginia. J. Environ. Qual. 4:
                        41-44.



























                                                                52









                                     Discharging Wastewater
                                                                                                                 a
                                     Treatm, ent Tec no ogies
                                                                                           Sand Filters













                          Virginia Department of Health
                      Office of Environmental Health Services















                                            PREFACE


                  The following report on sand filter technology was prepared as part of a
            training program for the Alternative Discharging Sewage Treatment System
            Regulations for Single Family Homes. The contents of this report were taken
            directly from the Environmental Protection Agency Publication entitled: Design
            Manual - Onsite Wastewater Treatment and Disposal Systems (October, 1980).
            The information in this EPA publication was used as a basis for sand filter
            training because it covers many aspects of sand filter design, construction, and
            use.


                  At the present time, "generic" plans and specifications for sand filter
            systems have not been developed by the Division of Onsite Sewage and Water
            Services. However, such generic plans will substantially follow the design
            standards and recommendations provided in the EPA Onsite Manual, as
            reproduced in this report. Until such time as "generic" plans and specifications
            are provided by the Division of Onsite Sewage and Water Services, the EPA
            manual should be used to guide you in the plan review process.


                                                              David Effert,
                                                              Technical Services Chi6f
                                                              July 24, 1992








                                                Intermittent Sand Filters'



                                                              Introduction


                         Intermittent sand filtration may be defined as the intermittent application of wastewater
                 to a bed of granular material which is underdrained to collect and discharge the final effluent.
                 One of the oldest methods of wastewater treatment known, intermittent sand filtration, if properly
                 designed, operated, and constructed, will produce effluent of very high quality. Currently, many
                 intermittent sand filters are used throughout the United States to treat wastewater from small
                 commercial and institutional developments and from individual homes. The use of intermittent
                 sand filters for upgrading stabilization ponds has also become popular.

                         Intermittent sand filtration is well suited to onsite wastewater treatment and disposal. The
                 process is highly efficient, yet requires.a minimum of operation and maintenance. Normally, it
                 would be used to polish effluent from septic tank or aerobic treatment processes and would be
                 followed by disinfection (as required) prior to reuse or disposal to land or surface waters.

                 Description

                         Intermittent sand filters are beds of granular materials 24 to 36 inches (61 to 91 cm) deep
                 and underlain by graded gravel and collecting tile. Wastewater is applied intermittently to the
                 surface of the bed through distribution pipes or troughs. Uniform distribution is normally
                 obtained by dosing so as to flood the entire surface of the bed.

                         Filters may be designed to provide free access (open filters), or may be buried in the
                 ground (buried filters). A relatively new concept in filtration employs recirculation of filter
                 effluent (recirculating filters).

                         The mechanisms of purification attained by intermittent sand filters are complex and not
                 well understood even today. Filters provide physical straining and sedimentation of solid
                 materials within the media grains. Chemical sorption also plays a role in the removal of some
                 materials. However, successful treatment of wastewater is dependent upon the biochemical
                 transformations occurring within the filter. Without the assimilation of filtered and sorbed
                 materials by biological growth within the filter, the process would fail to operate properly. There
                 is a broad range of trophic levels operating within the filter, from the bacteria to annelid worms.



                         'This material has been taken from the Environmental Protection Agency Design Manual for Onsite
                         Wastewater Treatment and Disposal Systems. U.S. Environmental Protection Agency, Office of Water
                         Programs Operation, Office of Research and Development, Municipal Environmental Research Laboratory.
                         Cincinnati, OH. EPA 625/1-80-012. October 1980. pgs. 113-140.









                        Since filters entrap, sorb, and assimilate materials in the wastewater, it is not surprising
                to find that the interstices between the grains may fill, and the filter may eventually clog.
                Clogging may be caused by physical, chemical, and biological factors. Physical clogging is
                normally caused by the accumulation of stable solid materials within or on the surface of the
                sand. It is dependent on grain size and porosity of the filter media, and on wastewater suspended
                solids characteristics. The prescription, coagulation, and adsorption of a variety of materials in
                wastewater may also contribute to the clogging problem in some filter operations. Biological
                clogging is due primarily to an improper balance of the intricate biological population within the
                filter. Toxic components in the wastewater, high organic loading, absence of dissolved oxygen,
                and decrease in filter temperatures are the most likely causes of microbial imbalances.
                Accumulation of biological slimes and a decrease in the rate of decomposition of entrapped
                wastewater contaminants within the filter accelerates filter clogging. All forms of pore clogging
                likely occur simultaneously throughout the filter bed. The dominant clogging mechanism is
                dependent upon wastewater characteristics, method and rate of wastewater application,
                characteristics of the filtering media, and filter environmental conditions.

                Application

                        Intermittent sand filtration is well adapted to onsite disposal. Its size is limited by land
                availability. The process is applicable to single homes and clusters of dwellings. The wastewater
                applied to the intermittent filters should be pretreated at least by sedimentation. Septic tanks
                should be required as a minimum. Additional pretreatment by aerobic biological processes
                normally results in higher acceptable rates of wastewater application and longer filter runs.
                Although extensive field experience is lacking to date, the application of pretreated graywaters
                to intermittent sand filters may be advantageously employed. There is some evidence that higher
                loading rates and longer filter runs can be achieved with pretreated graywaters.

                        Site constraints should not limit the application on intermittent sand filters, although odors
                from open filters receiving septic tank effluent may require isolation of the process from
                dwellings. Filters are often partially (or completely) buried in the ground, but may be constructed
                above ground when dictated by shallow bedrock or high water tables. Covered filters are
                required in areas with extended periods of subfreezing weather. Excessive long-term rainfall and
                runoff on submerged filter systems may be detrimental to performance, requiring appropriate
                measures to divert theses sources away ftom the system.


                                               Factors Affecting Performance

                        The degree of stabilization attained by an intermittent sand filter is dependent upon:

                                (1) the type of biodegradability of wastewater applied to the filter,
                                (2) the environmental conditions within the filter, and
                                (3) the design characteristics of the filter.



                                                                  2








                        Reaeration and temperature are two of the most important environmental conditions that
                affect the degree of wastewater purification through an intermittent sand filter. Availability of
                oxygen within the pores allows for the aerobic decomposition of the wastewater. Temperature
                directly affects the rate of microbial growth, chemical reactions, adsorption mechanisms, and
                other factors that contribute to the stabilization of wastewater within the sand media.


                        Proper selection of process design variables also affects the degree of purification of
                wastewater by intermittent filters. A brief discussion of those -variables is presented below.

                Media Size and Distribution

                        The successful use of a granular material as a filtering media is dependent upon the proper
                choice of size and uniformity of the grains. Filter media size and uniformity are expressed in
                terms of "effective size" and "uniformity coefficient." The effective size is the size of the grain,
                in millimeters, such that 10% by weight are smaller. The uniformity coefficient is the ratio of
                the grain size that has 60% by weight finer than itself to the size which is 10% finer than itself.
                The effective -size of the granular media affects the quantity of wastewater that may be filtered,
                the rate of filtration, the penetration depth of particulate matter, and the quality of the filter
                effluent. Granular media that is too coarse lowers the retention time of the applied wastewater
                through the filter to a point where adequate biological decomposition is not attained. Too fine
                a media limits the quantity of wastewater that may be successfully filtered, and will lead to early
                filter clogging. This is due to the low hydraulic capacity and the existence of capillary saturation,
                characteristic of fine materials. Metcalf and Eddy and Boyce recommended that not more than
                1% of the media should be finer than 0.13 mm. Recommended filter media effective sizes range
                from a minimum of 0.25 rm-n up to approximately 1.5 mm. Uniformity coefficients (UC) for
                intermittent filter media normally should be less than 4.0.

                        Granular media other than sand that have been used include anthracite, garnet, ilmenite,
                activated carbon, and mineral tailings. The media selected should be durable and insoluble in
                water. Total organic matter should be less than 1%, and total acid soluble matter should not
                exceed 3%. Any clay, loam, limestone, or organic material may increase the initial adsorption
                capacity of the sand, but may lead to a serious clogging condition as the filter ages.

                        Shapes of individual media grains include round, oval, and angular configurations.
                Purification of wastewater infiltrating through granular media is dependent upon the adsorption
                and oxidation of organic matter in the wastewater. To a limiting extent, this is dependent on the
                shape of the grain; however, it is more dependent on the size distribution of the grains, which
                is characterized by the UC.

                        The arrangement or placement of different sizes of grains throughout the filter bed is also
                an important design consideration. A homogeneous bed of one effective size media does not
                occur often due to construction practices and variations in local materials. In a bed having fine
                media layers placed above coarse layers, the downward attraction of wastewater is not as great
                due to the lower amount of cohesion of the water in the larger pores. The coarse media will not
                draw the water out of the fine media, thereby casing the bottom layers of the fine material to
                remain saturated with water. This saturated zone acts as a water seal, limits oxidation, promotes

                                                                  3






                clogging, and reduces the action of the filter to a mere straining mechanism. The use of media
                with a UC of less than 4.0 minimizes this problem.

                        The media arrangement of coarse over fine appears theoretically to be the most favorable,
                but it may be difficult to operate such a filter due to internal clogging throughout the filter.

                Hydraulic Loading Rate

                        The Hydraulic loading rate may be defined as the volume of liquid applied to the surface
                area of the sand filter over a designated length of time. Hydraulic loading is normally expressed
                as gpd/ft, or cm/day. Values of recommended loading rates for intermittent sand filtration vary
                throughout the literature and depend upon the effective size of sand and the type of wastewater.
                They normally range from 0.75 to 15 gpd/ft' (0.3 to 0.6 m'/M'/d).

                Organic Loading Rate

                        The organic loading rate may be defined as the amount of soluble and insoluble organic
                matter applied per unit volume of filter bed over a designated length of time. Organic loading
                rates are not often reported in the literature. However, early investigations found that the
                performance of intermittent sand filters was dependent upon the accumulation of stable organic
                material in the filter bed. To account for this, suggested hydraulic loading rates today are often
                given for a particular type of wastewater. Allowable loading rates increase with the degree of
                pretreatment. A strict relationship establishing and organic loading rate, however, has not yet
                been clearly defined in the literature.

                Depth of Media

                        Depths of intermittent sand filters were initially designed to be 4 to 10 feet; however, it
                was soon realized at the Lawrence Experimental Station that most of the purification of
                wastewater occurred within the top 9 to 12 in. (23 to 30 cm) of the bed. Additional bed depth
                did not improve the wastewater purification to any significant degree. Most media depths used
                today range from 24 to 42 in. (62 to 107 cm). The use of shallow filter beds helps to keep the
                cost of installation low. Deeper beds tend to product a more constant effluent quality, are not
                affected as severely by rainfall or snow melt, and permit the removal of more media before media
                replacement becomes necessary.

                Dosing Techniques and Frequency

                        Dosing techniques refer to methods of application of wastewater to the intermittent sand
                filter. Dosing of intermittent filters is critical to the performance of the process. The system
                must be designed to insure uniform distribution of wastewater throughout the filter cross-section.
                Sufficient resting must also be provided between dosages to obtain aerobic conditions. In small
                filters, wastewater is applied in doses large enough to entirely flood the filter surface with at least
                3 in. (8 cm) of water, thereby insuring adequate distribution, Dosing frequency is dependent
                upon media size, but should be greater with smaller doses for coarser media.




                                                                   4






                       Dosing methods that have been     . used include ridge and furrow application, drain tile
               distribution, surface flooding, and spray distribution methods. Early sand filters for municipal
               wastewater were surface units that normally employed ridge and furrow or spray distribution
               methods. Intermittent filters in use today are often built below the ground surface and employ
               tile distribution.


                       The frequency of dosing intermittent sand filters is open to considerable design judgement.
               Most of the earlier studies used a dosing frequency of I/day. The Florida studies investigated
               multiple dosings and concluded that the BOD removal efficiency of filters with media effective
               size greater than 0.45 mm is appreciably increased when the frequency of loading is increased
               beyond twice per day. This multiple dosing concept is successfully used in recirculating sand
               filter systems in Illinois, which employ a dosing frequency of once ever 30 min.

               Maintenance Techniques

                       Various techniques to maintain the filter bed may be employed when the bed becomes
               clogged. Some of these include:

                       (1) testing the bed for a period of time,
                       (2) raking the surface layer and thus breaking the inhibiting crust, or
                       (3) removing the top surface media and replacing it with clean media.

                         The effectiveness of each technique has not been clearly established in the literature.

               Filter Performance

                       (Sand filter effluent quality can be summarized as follows)...   intermittent filters produce
               high-quality effluent with respect to BOD, and suspended solids. Normally, nitrogen is
               transformed almost completely to the nitrate form provided the filter remains aerobic. Rates of
               nitrification may decrease in winter months as temperatures fall. Little or no denitrification
               should occur in properly operated intermittent filters.

                       Total and ortho-phosphate concentrations can      be reduced up to approximately 50% in
               clean sand; but the exchange capacity of most of the     sand as well as phosphorus removal after
               maturation is low. Use of calcareous sand or their high-aluminum or iron materials intermixed
               within the sand may produce significant phosphorus removal. Chowdhry and Brandes, et. al.,
               reported phosphorus removals of up to 90% when additions of 4% "red mud" (high in A1203 and
               Fe203)were made to a medium sand. Intermittent filters are capable of reducing total and fecal
               coliforms by 2 to 4 logs, producing effluent values ranging from 100 to 3,000 per 100 mil and
               1,000 to 100,000/100 ml for fecal and total coliforms, respectively.







                                                                 5






                                                           Design Criteria

                Buried Filters


                         Table I summarizes design criteria for subsurface intermittent sand filters.

                         Hydraulic loading of these filters is normally equ        Ial to or less than 1.0 gpd/ft' (0.04
                M'/m2/d) for full-time residences. This value is similar to loading rates for absorption systems
                in sandy soils after equilibrium conditions are obtained. When filters are designed for facilities
                with seasonal occupation, hydraulic loading may be increased to 2.0 gpd/ft' (0.08 m'/m2/d) since
                sufficient time will be available for drying and restoring the infiltrative surface of the bed.

                Table 1. Design Criteria For Buried Intermittent Sand Filters'



                           ITEM                                             DESIGN CRITERIA


                Pretreatment:                             Minimum level - sedimentation (septic tank or equivalent)

                Hydraulic Loading:
                  All year                                <L0 gpd/ft2
                  Seasonal                                <2.0 gpd/ft'

                Media:
                  Material                                Washed durable granular material (less than I percent organic
                                                           matter by weight)
                  Effective size                          0.50 to 1.00 mm
                  Unif Coeff.                             <4.0 (<3.5 preferable)
                  Depth                                   24 to 36 inches


                Underdrains:
                  Material                                Open joint or perforated pipe
                  Slope                                   0.5 to 1.0 percent
                  Bedding                                 Washed durable gravel or crushed stone (114 to 1-1/2 in.)
                  Venting:                                Upstream end


                Distribution:
                  Material                                Open Joint or perforated pipe
                  Bedding                                 Washed durable gravel or stone (3/4 to 2-1/2 in.)

                Venting:                                  Downstream end

                Dosing:                                   Flood filter; frequency greater than 2 times per day


                         'This material has been taken from the Environmental Protection Agency Design Manual for Onsite
                         Wastewater Treatment and Disposal Systems. U.S. Environmental Protection Agency, EPA 625/1-80-012.
                         October 1980. pg. 124. Virginia Department of Health design standards have not been established at
                         this lime*



                                                                     6







                         The effective size of media for subsurface filters ranges from 0.35 to 1.0 mm with a UC
                 less than 4.0, and preferably less than 3.5. Finer media will tend to clog more readily, whereas
                 coarser media may result in poorer distribution and will normally produce a lower effluent
                 quality.

                         Distribution and underdrains are normally perforated or open-joint pipe with a minimum
                 4-in. (10-cm) diameter. The distribution and underdrain lines are surrounded by at least 8 in. of
                 washed durable gravel or crushed stone. For distribution lines, the gravel or stone is usually
                 smaller than 2-1/2 in. (6 cm) but larger than 3/4 in. (2 cm), whereas the size range of the gravel
                 or stone for the underdrains is between 1-1/2 to 1/4 in. (3.8 to 0.6 cm). Slopes of underdrain
                 pipe range from 0.5 to 1%. With dosing, there would be no requirement for slopes on
                 distribution piping.

                         Proper dosing to the filter is critical to its successful performance. The dosing system is
                 designed to flood the entire filter during the dosing cycle. A dosing frequency of greater than
                 two times per day is recommended.


                 Free Access Filters (Non-Recirculating)

                         Design Criteria for ftee access filters are presented in Table 2.

                         Hydraulic loading to these filters depends upon media size and wastewater characteristics.
                 Septic tank effluent may be applied at rates up to 5 g-_od/ft2       (0.2 MI/M2  /d), whereas a higher
                 quality pretreated wastewater may be applied at rates as high as 10 gal/d ft' (40 cm/d). Selection
                 of hydraulic loading will also be influenced by desired filter run times. Higher acceptable
                 loadings on these filters as compared to subsurface filters relates primarily to the accessibility of
                 the filter surface for maintenance.


                         Media characteristics and underdrain systems for free access filters are similar to those
                 for subsurface filters. Distribution is often provided through pipelines and directed on splash
                 plates located at the center or comers of the sand surface. Occasionally, troughs or spray nozzles
                 are employed as well, and ridge and furrow application has been successful during winter
                 operation in severe climatic conditions. Dosing of the filter should provide for flooding the bed
                 to a depth of approximately 2 in. Dosing frequency is usually greater than two times per day.
                 For coarser media (greater than 0.5 mm), a dosing frequency greater than 4 times per day is
                 desirable.


                         The properties of the wastewater applied affect the clogging characteristics of the filter
                 and, therefore, the methods of filter maintenance. Dual filters, each designed to carry the design
                 flow rate, may be desirable when treating septic tank effluent to allow sufficient resting after
                 clogging.






                                                                     7







                 Table 2. Design Criteria For Free' Access Intermittent Sand Filters



                           ITEM                                           DESIGN CRITERIA


                 Pretreatment:                            Minimum level - sedimentation (septic tank or equivalent)

                 Hydraulic Loading:
                  Septic tank feed                        2.0 to 5.0 gpd/ft'
                  Aerobic feed                            5.0 to 10.0 gpd/ft'

                 Media:
                  Material                                Washed durable granular material (less than I percent organic
                                                             matter by weight)
                  Effective size                          0.35 to 1.00 mm
                  Unif Coeff.                             <4.0 (<3.5 preferable)
                  Depth                                   24 to 36 inches

                 Underdrains:
                  Material                                Open joint or perforated pipe
                  Slope                                   0.5 to 1.0 percent
                  Bedding                                 Washed durable gravel or crushed stone (1/4 to 1-1/2 in.)
                  Venting                                 Upstream end.

                 Distribution:                            Troughs on surface; splash plates at center or comers; sprinkler
                                                             distribution


                 Dosing:                                  Flood filter to 2 inches; frequency greater than 2 times per day

                 Number of filters:
                  Septic tank feed                        Dual filters, each sized for design flow
                  Aerobic feed                            Single filter


                         'This material has been taken from the Environmental Protection Agency Design Manual for Onsite
                         Wastewater Treatment and Disposal Systems. U.S. Environmental Protection Agency, EPA 625/1-80-012.
                         October 1980. pg. 126. Virginia Department of Health design standards have not been established at
                         this time.




                 Recirculating Filters

                         Proposed design criteria for recirculating intermittent sand filters are presented in Table
                 3. Theses free access filters employ a recirculation (dosing) tank between the pretreatment unit
                 and filter with provision for return of filtered effluent to the recirculation tank.




                                                                      8






                 Table 3. Design Criteria For Recirculating Intermittent Sand Filters'


                          ITEM                                                 DESIGN CRITERIA



                 Pretreatment:                              Minimum level - sedimentation (septic tank or equivalent)

                 Hydraulic Loading:                         3.0 to 5.0 gpd/ft' (forward flow)

                 Media:
                  Material                                  Washed durable granular material (less than I percent organic
                                                                matter by weight)
                  Effective size                            0.3 to 1.5 mm
                  Unif Coeff.                               <4.0 (<3.5 preferable)
                  Depth                                     24 to 36 inches


                 Underdrains:
                  Material                                  Open joint or perforated pipe
                  Slope                                     0.5 to 1.0 percent
                  Bedding                                   Washed durable gravel or crushed stone (1/4 to 1-1/2 in.)
                  Venting                                   Upstream end

                 Distribution:                              Troughs on surface; splash plates at center or comers; sprinkler
                                                            distribution


                 Recirculation Ratio:                       3:1 to 5:1 (5:1 preferable)

                 Dosing:                                    Flood filter to approx. 2 inches; pump 5 to 10 min per 30 min;
                                                                empty recirculation tank in less than 20 min

                 Recirculation Tank:                        Volume equivalent to at least one day's raw wastewater flow


                          'This material has been taken from the Environmental Protection Agency Design Manual for Onsite
                          Wastewater Treatment and Disposal Systems. U.S. Environmental Protection Agency, EPA 625/1-80-012.
                          October 1980. vg. 124. Virginia Department of Health design standards have not been established at
                          this time.



                          Hydraulic loading ranges from 3 to 5 gpd/ft2         (0.12 to 0.20 rn'/rr@/d) depending on media
                 size. Media size range is from 0.3 to 1.5 mm, the coarser sizes being recommended (23)(26).
                 Underdrain and distribution arrangements are similar to those for free access filters. Recirculation
                 is critical to effective operation, and 3:1 to 5:1 recirculation ratio (Recycle: Forward Flow) is
                 preferable.

                          Pumps should be set by timer to dose approximately 5 to 10 min per 30 min. Longer
                 dosing cycles may be desirable for larger installations - 20 min every 2 to 3 hr. Dosing should
                 be at a rate high enough to insure flooding of the surface to greater than 2 in. (5 cm).
                 Recirculation chambers are normally sized at 1/4 to 1/2 the volume of the septic tank.

                                                                        9








                                                    Construction Features


               Buried Filters


                       A typical plan and profile of a buried intermittent sand filter are depicted in Figure 1.
               The filter is placed within the ground with a natural topsoil cover in excess of 10 in. (25 cm)
               over the crown of the distribution pipes. The filter must be carefully constructed after excavation
               and the granular fill settled by flooding. Distribution and underdrain lines should be constructed
               of an acceptable material with a minimum diameter of 4 in. (10 cm). The tile is normally laid
               with open joints with sections space not less than 1/4 inc. (0.6 cm) or greater than 1/2 in. (1.3
               cm) apart. If continuous pipeline is used, conventional perforated pipe will provide adequate
               distribution and collection of wastewater within the filter.


                       The underdrain lines are laid to grade (0.5 to 1%) and one line is provided for each 12
               ft (3.6 m) of trench width. Underdrains are provided with a vent pipe at the upstream end
               extending to the ground surface. The bedding material for underdrain lines in usually a minimum
               of 10 in. (25 cm) washed graded gravel or stone with sizes ranging from 1/4 to 1-1/2 in. (0.6 to
               3.8 cm). The gravel or stone may be overlain with a minimum of 3 in. (8 cm) of washed pea
               gravel (1/4 - to 3/8 in. [1.9- to 6.3-cm] size) is usually employed for bedding of distribution lines.
               Marsh hay, washed pea gravel, or drainage fabric should be placed between the bedding material
               and the natural topsoil.

                       The finished grade over the filter should be mounded so as to provide drainage of rainfall
               away from the filter bed. A grade of approximately 3 to 5%, depending upon topsoil
               characteristics, would be sufficient.

                       Any washed, durable granular material that is low in organic matter may be used for filter
               medium. Mixtures of sand, slag, coal, or other materials have been used to enhance the removal
               of selected pollutants and to extend filter life. Care must be taken, however, to insure that the
               media does not stratify with fine layers over coarse.

               Free Access Filters


                       The plan and profile of a typical free access    filter appear in Figure 2. These filters are
               often built within the natural soil, but may also be constructed completely above the ground
               surface. They are usually surrounded by sidewalls,       often of masonry construction, to prevent
               earth from washing into the filter media and to confine the flow of wastewater. Where severe
               climates are encountered, filter walls should be insulated if exposed directly to the air. The floor
               of the filter is often constructed of poured concrete or other masonry, but may consist of the
               natural compacted soil. It is usually sloped to a slight grade so that effluent can be collected into
               open joint or perforated underdrains.






                                                                 10









                      Figure 1. Typical Buried Intermittent Sand Filter System



                                                                       Vent Pipe





                                                                                                  . . . . . .. . . . . .. . . . . .
                                                                                            .... ..... . ......
                                                            . ......                                               Discharge
                                                                                     .............

                                                          am,
                                                           ------------ It'll
                                               D-box
                           Septic Tank                            Buried Sand       Filter
                                                                                                 Inspection Manhole
                                                                                                   and Disinlection
                                                                Profile View                         Contact Tank
                                                                                                         (no detail)









                                                                                Top Soil Fill





                                                                                                     > 6" top Soil fill
                                                                                                     > 8" 3/4" - 2 1/2u gravel


                       Drainage Fabric
                                                                                                     24" - 360 sand

                                Perforated                       ...... I .......
                                                                                                     31 pea gravel
                              Pipe (4' typ.

                                                                                                     > 81 3/4"
                                                                                                                    2 1/2" gravel



                                                                 Section View




                                                                                                                   Not To Scale
                                                                                                            Not All Details Are Shown





                 Figure 2. Free Access Intermittent                  Sand Filter Plan and Cross Section View




                                                                                                  Splash Plate



                                                                               .............

                                                                                 ... .. .........

                                                                          M
                                                                      .. .... .......

                                                                                                      Discharge
                      Discharge
                                                                                           .... . .-----
                                                              ... .......




                                                                           .. . ...... ....



                                                         ... .... . ..





                              Distribution                       Valve
                                  Pipe                                                                         From
                                                                                                               SeDtic Tank


                                                                 Plan View




                                             Distribution Pipe     Vent Pipe        Distribution Pipe
                                Cover

                                                      Er'                      0                         \IV

                                                                                     . .........



                                                                                                            242 - 36 0 sand


                                                                                       ..............
                                                      . . . . . .. . . . .
                                                ... .........
                                                                                      .. .........


                                                                                                            4* pea gravel
                                                                                                            10' #57 gravel




                                                          Perforated Collection Pi
                                                               to discharge
                                                                                11pe



                                                         Cross Section                                      Not To Scale
                                                                                                       Not All Details Are Shown
                                                                                                           (DDEf7-20-92)
                                                                         12






                        Free access filters may be covered to protect against severe weather conditions, and to
                avoid encroachment of weeds or animals. The cover also serves to reduce odor conditions.
                Covers may be constructed of treated wooden planks, galvanized metal, or other suitable material.
                Screens or hardware cloth mounted on wooden frames may also serve to protect filter surfaces.
                Where weather conditions dictate, covers should be insulated cover and sand surface.

                        The underdrain lines should be constructed of an acceptable material with a minimum
                diameter of 4 in. (10 cm). The tile is normally laid so that joints are spaced not less than 1/4 in.
                (0.6 cm) or greater than 1/2 in. (1.3 cm) apart. Conventional perforated pipe may also be
                employed for distribution and collection. The underdrain lines may be laid directly on the filter
                floor, which should be slightly pitched to carry filtered effluent to the drain line. In shallow
                filters, the drain line may be laid within a shallow trench within the filter floor. Drain lines are
                normally spaced at 12-ft (3.6-m) centers and sloped at approximately 0.5 to 1% grade to
                discharge. The upstream end of each drain line should be vented with a vertical vent pipe above
                the filter surface, but within the covered space.

                        The bedding material for underdrain lines should be a minimum of 10 in. (25 cm) of.
                washed graded gravel or stone with sizes ranging from 1/4 to 1-1/2 in. (0.6 to 3.8 cm). The
                gravel or stone may be overlain with a minimum of 3 in. (8 cm) of washed pea gravel interfacing
                with the filter media.


                        Distribution to the filter may be by means of troughs laid on the surface, pipelines
                discharging to splash plates located at the center or comers of the filter, or spray distributors.
                Care must be taken to insure that lines discharging directly to the filter surface do not erode the
                sand surface. The use of curbs around the splash plates or large stones placed around the
                periphery of the plates will reduce scour. A layer of washed pea gravel placed over the filter
                media may also be employed to avoid surface erosion. This practice will create maintenance
                difficulties; however, when it is time to rake or remove a portion of the media surface.

                        Filter media employed in free access filters may be any washed, durable granular material
                free of organic matter. As indicate previously for buried filters, mixtures of sand, slag, coal, or
                other materials may be employed, but with caution.

                Recirculating Filters

                        A profile of a typical recirculating sand filter system is presented in Figure 3.
                Recirculating filters are normally constructed with free access to the filter surface. The elements
                of filter construction are identical to those for the free access filter.


                        The basic difference between the recirculating filter and the free access filter is the
                recirculation chamber (dosing chamber) which incorporates a pump to recycle filter effluent. The
                recirculation tank receives the overflow from a septic tank, as well as a portion of sand filter
                effluent. A pump, controlled by a time clock mechanism, pumps the wastewater mixture to the
                filter surface. The recirculation tank is of equivalent strength and material to the septic tank. It
                is normally 1/4 to 1/2 the size of the septic tank (or a volume equivalent to at least one day's
                volume of raw wastewater flow). The tank must be accessible for maintenance of pumps, timers,
                and control valves. Covers should be provided and insulated as required by climatic conditions.

                                                                 13






                                  Figure 3. Typical Recirculating Sand Filter System (Using Splitter Box)



                                                                                                                              n        n

                                                                                                       Returning
                                                                                                                                .............
                                                                                                                                ...........
                                                                                                        Filtrate

                                                                               Effluent
                                                                     optic      Pump
                                                                     Tank                                               Free Access
                                                                   Efflu nt
                                                                     Flow                                                Sand Filter
                                           Septic Tank                          Recirculation              arging      Splitter Box
                                                                                     Tank              Filtrate







                                         4. Cross-section Of A Recirculating Tank Using A Float Valve










                                                                          ------- -----



                                                                     Liquid Level                                                     From Filter
                                                                           Discharge J@
                                                                                                                                      To Filter



                                                                                         Float
                                                                                         Valve



















                                                                                                                                               W TO Sews
                                                                                                                                          Not All Doak Am Shown


                                                                                                                                              OMW-204M
                                                                                       14







                        Recirculation ratios may be controlled by a variety of methods. These include splitter
                boxes, moveable gates, check valves, and a unique "float valve" arrangement (Figure 4). The
                "float valve" incorporates a simple tee and a rubber ball suspended in a wire basket. The ball
                will float up and close off the inverted tee when the water level rises. Recirculation rations are
                normally established between 3:1 to 5:1.

                        Recirculation pumps are normally submersible pumps rated for 1/3 horsepower. They
                should be sized to empty the recirculation tank in less than 20 min. The recirculation pump
                should be controlled by a time clock to operate between 5 to 10 min every 30 min, and should
                be equipped with a float shut-off and high water override.


                                                 Operation and Maintenance

                General


                        Intermittent sand filters require relatively little operational control or maintenance. Once
                wastewater is applied to the filter, it takes from a few days to two weeks before the sand has
                matured. BOD and SS concentrations in the effluent will normally drop rapidly after maturation.
                Depending upon media size, rate of application, and ambient develop. Winter start-up should be
                avoided since the biological growth on the filter media may not properly develop.

                        As discussed above, clogging of the filter eventually occurs as the pore space between the
                media grains begins to fill with inert and biological materials. Once hydraulic conductivity falls
                below the average hydraulic loading, permanent ponding occurs. Although effluent quality not
                initially suffer, anaerobic conditions within the filter result in further rapid clogging and a
                cessation of nitrification. Application of wastewater to the filter should be discontinued when
                continuous ponding occurs at levels in excess of 12 in. (30 cm) above the sand surface. A high
                water alarm located 12 in. (30 cm) above the sand surface serves to notify the owner of a ponded
                condition.


                        Since buried filters cannot be easily serviced, the media size is normally'large and
                hydraulic application rates are low (usually less than 2 in./d [5 cm/d]). Proper pretreatment
                maintenance is of paramount importance. Free access filters, on the other hand, may be designed
                with finer media and at higher application rates. Experience indicates that intermittent sand filters
                receiving septic tank influent will clog in approximately 30 and 150 days for effective sizes of
                0.2 mm and 0.6 mm, respectively. Aerobically treated effluent can be applied at the same rates
                for up to 12 months if suspended solids are under 50 mg/l. Results with recirculated filters using
                coarse media (1.0 - 1.5 min) indicate filter runs in excess of one year.

                Maintenance of Media

                        Maintenance of the media includes both routine maintenance procedures and media
                regeneration upon clogging. These procedures apply to free access filters only. The effectiveness
                of routine raking of the media surface has not been clearly established, although employed in


                                                                 15







                several studies. Filters open to the air require weed removal as well.. Cold weather maintenance
                of media may require different methods of wastewater application, including ridge and furrow
                and continuous flooding. These methods are designed to eliminate ice sheet development. Use
                of insulated covers permits trouble-free winter operation in areas with ambient temperatures as
                low as -40* F.


                       Eventually, filter clogging requires media regeneration. Raking of the surface will not in
                itself eliminate the need for more extensive rehabilitation. The removal of the top layer of sand,
                as well as replacement with clean sand when sand depths are depleted to less than 24 to 30 in.
                (61 to 76 cm), appears to be very effective for filters clogged primarily by a surface mat. This
                includes filters receiving aerobically treated effluent. In-depth clogging, however, often prevails
                in many intermittent filters requiring oxidation of the clogging materials. Resting of the media
                for a period of time has proven to be very effective in restoring filter hydraulic conductivity.
                Hydrogen peroxide treatment may also prove to be effective, although insufficient data are
                available on long-term application of this oxidizing agent.


                Other Maintenance Requirements

                       The successful operation of filters is dependent on proper maintenance of the pretreatment
                processes. The accumulation of scum, grease, and solid materials on the filter surface due to
                inadequate pretreatment results in premature filter failure. This is especially critical for buried
                filters. Grease traps, septic tanks, and other pretreatment processes should be routinely
                maintained in accordance with requirements listed in other sections of this manual.

                       Dosing chambers, pumps, and siphons should receive periodic maintenance checks. If
                electronic sensing devices are employed to warn owners of filter ponding, these devices should
                also be periodically checked as well.


                                                   Maintenance Summary

                       The maintenance and operational requirements for buried, free access and recirculating
                filters are summarized in Tables 4, 5, and 6. Routine maintenance requirements have not been
                well documented for intermittent filtration onsite, but visits should be made four times per year
                check filters and their appurtenances.      Based on meager data base, unskilled manpower
                requirements for buried filter systems would be less than 2 man days per year for examination
                of dosing chamber and appurtenances and septic tank. Free access filters may require from 2 to
                4 days per year for media maintenance and replacement and examination of dosing chamber,
                septic tank, and appurtenances. Additional time would be required by analytical technicians for
                effluent quality analysis as required. Power requirements would be variable, depending upon the
                dosing method employed, but should be less than 0.1 kV;h/day. The volume of waste media
                from intermittent filters may amount to approximately 0.25     ftl/ft2 (0.08 MI/M2) of surface area
                each time media must be removed.


                                                                16









                Table 4. Operation And Maintenance Requirements For A Buried Intermittent Sand Filter


                          ITEM                                          O/M REQUIREMENTS


                Pretreatment:                                           Depends upon process

                Dosing Chamber:
                 Pumps and controls                                     Check every 3 months
                 Timer sequence                                         Check and adjust every 3 months
                 Appurtenances                                          Check every 3 months

                Filter Media:                                           None





                Table 5. Operation And Maintenance Requirements For A Free Access Intermittent Sand
                            Filter



                          ITEM                                          O/M REQUIREMEND


                Pretreatment:                                   Depends upon process

                Dosing Chamber:
                 Pumps and controls                             Check every 3 months
                 Timer sequence                                 Check and adjust every 3 months
                 Appurtenances                                  Check every 3 months


                Filter Media:
                 Raking                                         Every 3 months, 3 in. deep
                 Replacement
                   -Septic Tank feed                            Replace when ponded more than 12 in. deep; replace
                                                                   top 2 to 3 in. sand; rest while alternate unit in
                                                                   operation (60 days)
                   -Aerobic feed                                Replace when ponded more than 12 in. deep; replace
                                                                   top 2 to 3 in. sand; return to service

                Other:                                          Weed as required; maintain distribution device as
                                                                   required; protect against ice sheeting; check high
                                                                   water alarm





                                                                   17











                Table 6. Operation And Maintenance Requirements For Recirculating Intermittent Sand
                           Filters



                         ITEM                                      OIM REQUIREMENTS


                Pretreatment:                               Depends upon process

                Dosing Chamber:
                 Pumps and controls                         Check every 3 months
                 Timer sequence                             Check and adjust every 3 months
                 Appurtenances                              Check every 3 months

                Filter Media:
                 Raking                                     Every 3 months skim sand 3 in, deep when heavy
                                                               incrustation occur;
                 Replacement                                Add new sand when sand depth falls below 24 in.

                Other:                                      Weed as required; maintain distribution device as
                                                               required; protect against ice sheeting

























                                                              18





                 Desi*gn and Installati*on
                                                                                     0
                o'f LowmPressure Pipe
                 VVaste Treat ent Syste s




                                                                                         Ile-













                 Craig Cogger        Bobby L Carlile Dennis Osborne                 Ed Holland















                 UNC Sea Crant r-Ifege Publication UNC-SG-82-03
                 Ma    q R?






             Des'iogn and Installation
             of LowmPressure Pi*pe
             Waste Treat ent Syste                                                                     s





             Written by Craig Cogger, Bobby L Carlile and Dennis Osborne
             North Carolina State University
             Department of Soil Science

             Ed Holland
             Triangle) Council of Governments




             Designed and edited by Kathy Hart
             UNC Sea Grant College Program

             Illustrated by Timothy Howard
                                                                                                lb      z
             Cover Photo by Neil Caudle

                                                                                              MT


             UNC Sea Grant College Publication UNC-SG-82-03
             May 1982




                   LPP Design and installation on Sloping Ground-21
                   Layout-21
                   Dosing and distribution-21
                       p selection-22
                   Design of split manifold systems-25
                   Pum


                   Modified LPP Systems Using Fill-26
                   Modified LPP design-26
                   Installation-26
                   inspection and Maintenance-27
                   Installation inspection-27
                   Operation inspections-27
                   Routine maintenance-27
                   Repair procedures-27
                   Appendixes-28
                   Design specifications for example LPP-28
                   Pipe and fittings for example LPP-29
                   Other supplies for example LPP-29
                   LPP construction inspection checklist-30
                   Maintenance checklist-31





           Introduction





             Many sites under consideration for develop-             other ground absorption systems. Many engineers,
           ment in North Carolina are not suitable foron-site.       sanitarians, contractors and designers are unfa-
           sewage disposal by conventional septic systems.           miliar with LPP construction, and these instructions
           Among these sites are some which do have                  are designed as an aid to them. Although those
           enough depth and area of usable soil to provide           who design, build and use septic systems can
           safe disposal via low-pressure pipe (LPP) systems.        benefit from this report, it must always be used in
           LPP systems are not a panacea for all the unsuitable      cooperation with the local health department.
           soils of North Carolina, but they are useful      for     The local health department must first approve a
           some specific conditions where conventional               site, and then assign waste flow and soil loading
           systems have frequently failed.                           rates.
             This manual specifies the procedures and ma-              This manual covers design and installation of
           terials to be used for successful siting, design,         small LPP systems suitable for homes and small
           installation and maintenance of residential LPP           businesses. Principles are similar for larger com-
           systems. Use of proper materials and techniques           mercial and institutional systems, but the special
           is critical to the success of the LPP, as well as to all  requirements of those systems are not addressed.




                  CHAPTER 1
                  What Is Low-Pressure Pipe
                  Distribution?



                    A soil-absorption system must serve two pur-            horizon or seasonally high-water table.
                  poses: 1) keep untreated effluent below the                 An LPP system is a shallow, pressure-dosed soil-
                  surface, and 2) purify the effluent before it reaches     absorption system (Figure 1). It consists of:
                  ground or surface water. The system works best            * two-compartment septic tank
                  when the distribution area is not saturated with          9 pumping chamber
                  water or effluent, allowing efficient aerobic bac-        * submersible effluent pump and level controls
                  teria to treat the wastes.                                9 high-water alarm
                    There are several conditions which frequently           * supply line and manifold
                  hinder the operation of soil-absorption systems.          * distribution laterals
                  Clogging of the soil can occur from localized over-       e suitable area and depth of soil
                  loading during use or from the mechanical sealing         When septic tank effluent rises to the level of the
                  of the soil-trench interface during construction    '     upper pump control, the pump turns on and
                  This clogging can cause effluent to break through         effluent moves through the supply line and distri-
                  to the surface, especially in fine-textured soils.        bution laterals. These laterals are PVC pipes
                  Anaerobic conditions caused by continuous sat-            containing small holes Na inch to 1/4 inch) spaced
                  uration due to overloading or a high-water table          three to five feet apart. The pipes are placed in
                  retard treatment, increasing the potential for            narrow trenches six to 18 inches deep, spaced
                  pollution. Shallow soils are not deep enough to           five or more feet apart. Under low pressure [0.7 to
                  purify the effluent.                                      twopounds persquare inch (psi)] supplied bythe
                    The LPPsystem hasthreedesign improvements               pump, septic tank effluent flows through the
                  to help overcome these problems. These are:               holes and into the trenches. It diffuses from the
                  ï¿½ uniform distribution of effluent                        trenches into the soil where it is treated.
                  ï¿½ dosing and resting cycles                                 The pump turns off when the effluent level falls
                  ï¿½ shallow placement of trenches                           to the lower control. The level controls are set
                  Problems from local overloading     are decreased         so that the efflue--t is pumped two to four times
                  when effluent is distributed over    the entire ab-       daily with restin Periods in between to allow
                  sorption area. Dosing and resting cycles help             aerobic treatment of effluent. If thepumpor level
                  maintain aerobic conditions in the soil, improving        controls should fail, the effluent would rise to the
                  treatment. Shallow placement increases the ver-           level of the alarm control-The alarm would turn
                  tical separation from the system to any restrictive       on, signaling the homeowner of failure.







                                                                      "4#ss ;R.5eR











                    -%AO-                       Pun7Q&     K
                    sd?74 -4@414



                  Figure 1. Basic components of a low pressure pipe system


                  2





               CHAPTER 2
               Site and Soil Requirements
               for LPP System's


                 The suitability of an LPP system for a given site is      procedures (Chapter 7). The distribution field of
               determined [- -; the soil, slope and available space,       any LPP system should be at an elevation equal to
               as well as by the anticipated waste flow. The               or higher than the pumping chamber. This prevents
               criteria below are a set of practical guidelines            the gravity flow or inadvertent siphoning of effluent
               that may be modified by individual county health            from the pump chamber to the field when the
               departments.                                                pump is not operating. If the field must be lower
                                                                           than the pump tank, then the system must be
               Space requirements                                          designed to ensure that effluent cannot leave the
                 The distribution network      of most residential         pump chamber when the pump is turned off.
               LPP systems occupies from      1000 square feet to          Drainage requirements
               5000 square feet of area depending on the soil
               permeability and design waste load. In addition,              Depressions, gullies, drains and erosional areas
               an area of equal size must be set aside for future          must be avoided to prevent hydraulic overloading
               repair or replacement of the system. Space be-              by surface runoff. Neither the septic tank, pumping
               tween the existing lateral lines is not a suitable          chamber nor distribution field should be located
               repair area, unless the initial spacing between             in such areas. Surface water and perched ground-
               lines is 10 feet or wider. The septic tank, pumping         water must be intercepted or diverted away from
               chamber, distribution field and repair area are             all components of the LPP system.
               also all subject to horizontal setbacks from wells,
               property lines, building foundations, etc., as spe-
               cified in local or state regulations [10 NCAC
               10A .191 2(a)]. Although it is not feasible to inte-
               grate all of the site and soil setback criteria into a
               general lot size requirement, an undeveloped lot
               smaller than one acre will not usually be acceptable
               for an LPP system.
               Soil requirements
                 An LPP system should be situated on the best
               soil and site on the lot. A minimum of 12 inches of
               usable soil is required between the bottom of the
               absorption field trenches and any underlying
               restrictive horizons such as consolidated bedrock
               or hardpan, or to the seasonally high, water table.
               LPP trenches can be placed as shallowly as eight
               to 12 inches deep,'giving a minimum soil-depth
               requirement of 20 to 24 inches. The soil must be
               of suitable or provisionally suitable texture, struc-
               ture and permeability, as defined in state regula-
               tions 0 0 NCAC 1 OAA 920). In some cases where
               the depth to the seasonal water table or restrictive
               horizons is less, a modified LPP may be installed
               using imported fill. Great care must be used in
               building these systems. Their design and con-
               struction are covered in Chapter 8.
               Topography
                 Low-pressure distribution fields located on
               slopes require special design and installation

                                                                                                                                3




                     CHAPTER 3
                     Layout of an LPP System




                      The next three chapters are a step-by-step                       Example:
                     procedure for designing an LPP system. There is                   For a sandy clay loam:
                     no one LPP that fits all sites-each must be                       Loading rate = 0.25 gpd/ft'
                     designed individually. Additional procedures used
                     when designing LPP systems on sloping sites and                   Note: Waste flow and loading rates must be
                     where fill is used are covered in Chapters 7 and 8.               determined by the local health department
                                                                                       before the LPP system can be designed.
                     Size of the absorption area                                       Step 3. Compute the total area needed for the
                     The total amount of absorption area depends on                    absorption system us     Ing the equation: Area
                     two factors-the daily wastewater flow of the                      flow/loading rate.
                     system and the absorptive capacity of the soil.
                        Step 1. Calculate daily waste flow. For residen-               Example:
                        tial systems, the estimated flow is 150 gallons                Using flow and loading rates calculated above:
                        per day (gpd) for each bedroom (BR) in the                     Area = 450 gpd/0.25 gpd/ft' = 1800 it'
                        house.
                        Example:                                                       Step 4. Determine total length of distribution
                        For a 3-BR house:                                              lines. Spacing between lines must be five
                        Flow = 150 gpd/BR x 3 BR = 450 gal                             feet or more to prevent overloading. Divide
                                                                                       total area by five to obtain the total length of
                        Step 2. Determine the loading rate. Estimate                   the distribution lines.
                        soil permeability during the field evaluation
                        and determine the wastewater- loading rate                     Example:
                        using Table 1.                                                 Length = 1800 ftI/5 it = 360 it



                   Table 1. Maximum loadFng rates for LPP systems based on soil texture and estimated permeability

                      USDA Soil Texture*                            Estimated Permeability                       Maximum Loading Rate**
                                                                           minlin.                                         _qpdlft2
                   Sand, loamy sand                                          20                                          0.50-0.40

                   Sandy loam, silt loam                                   20-40                                         0.40-0.30

                   Sandy clay loam, clay loam                              40-60                                         0.30-0.20

                   Silty clay loam, sandy clay                             60-90                                         0.20-0.10

                   Silty clay, clay                                        90-120                                        0.10-0.05


                     *This table does not consider the effects of clay mineralogy on soil permeability. A sandy clav composed of 1: i clavs may be more
                     permeable than a clay loam of 2:1 clays.
                   "These loading rates should be used only for calculating the size of LPP systems-not for other types of s\,stems.





                   4





                 Step 5. Calculate gravel requirements. To fi I I a
                 six-inch wide trench six inches deep with
                 gravel, 1.5 yards (1.9 tons) is needed per 100
   k             feet of line.

                 Example:
                 For 360 ft of line:
                 Gravel needed = (360 ft/100 ft) x 1.5 yds
                                   = 5 yds
             Size of septic and pumping tanks
               Septic-tank volume is determined according to
             state and local regulations, and is the same as a
             conventional system. The pumping tank should
             provide one day for emergency storage; thus, it
             should be at least twice the volume M of the
             daily waste flow.

                 Example:
                 For a 450 gpd waste flow:
                 V pumping tank = 450 gal x 2 = 900 gal

             Location of system
               The LPP should be located in the best available
             soil on the lot. All setback requirements from
             wells, lot lines and waterways must be observed.
             The exact location of the tanks as well as drainage
             and landscaping improvements must be noted. A
   0         repair or replacement space on suitable soil equal
             in area to the absorption field must be located.
             Shape of absorption field
               When selecting the best shape         to fit in the
             desired location, lines must be placed on the
             contour. Also, lines should not extend more than
             70 feet from the manifold (supply line) due to
             excessive friction loss. When using larger lateral
             lines, the manifold must be placed in the centerof
             the distribution system rather than along the side
             (Figure 2). For a layout example, see Figure 3.
             Landscaping and drainage
               All landscaping, filling and site drainage to be
             done before and afterthe LIPP installation must be
             recorded in detail on the improvements permit.
             Depth of lines
               Lines are normally placed 18 inches deep.
             Shallower placement will be necessary in soils
             with shallow water tables, bedrock or restrictive
             horizons in order to meet the one-foot vertical
             separation requirement.

































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                                           C, cc-Q@@R                              zo,                       F12





                 Figure 2. Three possible shapes of an 1800 ft' LPP distribution field


                 6



















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                                                                                                        40 0







                                                                                                           te. @OU.5t











             Figure 3. Layout of a sample system




                 CHAPTER 4
                 Dosing and Distribution                                                                                                           7)
                 System Design



                   The purpose of low-pressure dosing is to provide                   Example:
                 uniform distribution of septic tank effluent over                    For a system with 5-ft hole spacing and six
                 the entire soil-absorption system. This is best                      60-ft lines:
                 achieved at a pressure head of two to four feet                      No. holes/line = 60 ft/5 Whole
                 (0.9 to 1.7 psi). Lower pressures do not provide                                       = 12 holes/line
                 uniform delivery of effluent. Higher pressures                       Total holes = 12 holes/line x 6 lines
                 cause local scouring of the gravel and soil in the                                 = 72 holes
                 trench bottoms. The proper dosing involves bal-
                 ancing the size of the distribution system with the                  Step 2. Determine the flow rate per hole. This
                 closingvolume, pumping capacity, desired pressure                    is calculated from the hole size and pressure
                 and flow rate.                                                       head using Table 2.
                 Dosing rate                                                          Example:
                   The dosing rate depends on the pressure head                       For 3-ft pressure    head and 5/32-inch holes:
                 and the size and number of holes in the distribution                 Flow rate = 0.50     gallons per minute (gpm)
                 lines. Pressure head can range from two to four
                 feet for adequate performance; holes must be Ma                      Step 3. Calculate    total dosing rate.
                 inch or greater in diameter, and hoi spacing can
                 range from three to five feet. On s ping lots, it                    Example:
                 may be necessary to have holes as small as 3/32                      Flow rate/hole       0.50 gpm
                 inch and spacing greater than five feet, in a part,                  Flow rate/line       0.50 x 12 holes      6.0 gpm
                 but not in all of the system as explained in                         Total flow rate      0.50 x 72 holes       36 gpm
                 Chapter 8. The best startingvalues forcalculation
                 are a 5/32-inch hole diameter, five-foot hole
                 spacing and three feet of pressure head.                           For systems where the absorption field is at a
                     Step. 1. Calculate the number (no.) of holes.               lower elevation than the pump, a 1/4-inch siphon-
                     No. holes = length of line/hole spacing                     breaker hole must be drilled in the supply line in




                 Table 2. Flow rate as a function of pressure head and hole diameter in drilled PVC pipe

                      Pressure                                                        Hole diameter (in.)
                        Head                         3/32                 1/8               5/32                 3/16                 7/32

                 ft              psi                                                   Flow rate (gpm) -

                 1               0.43                0.10               0.18                0.29                 0.42                 0.56

                 2               0.87                0.15               0.26                0.41                 0.59                 0.80

                 3               1.30                0.18               0.32                0.50                 0.72                 0.98

                 4               1.73                0.21               0.37                0.58                 0.83                 1.13

                 5               2.16                0.23               0.41                0.64                 0.94                 1.26





                 8





                the pumping tank. This hole will prevent inadver-                     Elevation head is the difference in elevation
                tent siphoning of the contents of the pump tank                     from the pump to the end of the manifold.
                into the field. An extra two gallons per minute                     Remember that the pump will be four feet or five
                must be added to the pumping rate to compensate                     feet below ground level i n the pum ping chamber.
                for flow through the siphon-breaker hole.                             Pressure head is the pressure required for even
                                                                                    distribution and is usually specified between two
                    Example:                                                        and four feet.
                    For a system with 36 gpm flow rate and a                          Friction head is the loss of pressure due to
                    siphon-breaker hole.                                            friction as the effluent moves down the pipes.
                    Total flow rate = 36 gpm + 2 gpm = 38 gpm                       Pipe friction is estimated using Table 3. When
                                                                                    estimating pipe friction, use the length of the
                Pump selection                                                      supply manifold, but not the lateral lines. Add 20
                                                                                    percent to the pipe friction estimate to account
                   The pump must have enough power to pump                          for friction loss in joints and fittings. Note that
                effluent at the calculated flow rate against the                    friction loss varies with pumping rate as well as
                total head (resistance) encountered in the distri-                  with pipe length and diameter.
                bution system. The total head is the amount of                        The total head must be calculated to select the
                work the pump must do to overcome elevation                         proper size pump.
                (gravity) and friction in the system at the specified
                pressure and flow rate. Total head = elevation                          Step 1. Compute friction head.
                head + pressure head + friction head.                                   Friction head        1.2(pipe friction)



                Table 3. Friction loss per 100 feet of PVC pipe

                                                                                Pipe diameter (in.)
                Flow                 1                   1 '/4                1 Y2                  2                     3                    4

                gpM                                                              Friction loss (ft)

                   1              0.07
                   2              0.28                 0.07
                   3              0.60                 0.16                  0.07
                   4              1.01                 0.25                  0.12
                   5              1.52                 0.39                  0.18
                   6              2.14                 0.55                  0.25                 0.07
                   7              2.89                 0.76                  0.36                 0.10
                   8              3.63                 0.97                  0.46                 0.14
                   9              4.57                 1.21                  0.58                 0.17
                10                5.50                 1.46                  0.70                 0.21
                11                                     1.77                  0.84                 0.25
                12                                     2.09                  1.01                 0.30
                13                                     2.42                  1.17                 0.35
                14                                     2.74                  1.33                 0.39
                15                                     3.06                  1.45                 0.44                0.07
                16                                     3.49                  1.65                 0.50                0.08
                17                                     3.93                  1.86                 0.56                0.09
                18                                     4.37                  2.07                 0.62                0.10
                19                                     4.81                  2.28                 0.68                0.11
                10
                                                       5.23                  2.46                 0.74                0.12
                25                                                           3.70 5               1.10                0.16
                30                                                           5.22                 1.54                0.23
                35                                                                                2.05                0.30                 0.07
                40                                                                                2.62                0.39                 0.09
                45                                                                                3.27                0.48                 0.12
                50                                                                                3.98               "0.58                 0.16
                60                                                                                                    0.81                 0.21
                70                                                                                                    1.08                 0.28
                80                                                                                                    1.38                 0.37
                90                                                                                                    1.73                 0.46
                '00                                                                                                   2.09                 0.55



                                                                                                                                               9






                    Example:                                                        intersect at a point which must fall below the
                    For a 70ft supply line with a 2-in. diameter                   performance curve. if the point falls above
                    and a 36-gpm pumping rate:                                      the curve, then the pump is too small.
                    Pipe friction =   (70 ft/100 ft) x 2.2 ft                       Example:
                                  =    1.5 ft
                    Friction head  =    1.2 x 1.5 ft                                This point in Figure 4 falls below the curve;
                                   =    1.8 ft                                   therefore, the pump is adequate.
                    Step 2. Calculate total head.                                 When the chosen pump is too small, there are
                    Example:                                                   several options to consider:
                    For a system     with 5-ft elevation head from               Select a larger pump.
                    pump to end of the lines, 3-ft pressure head,                Reduce the total head requirement, by reducing
                    1.8-ft friction  head:                                       the pressure head (two feet is the minimum).
                    Total head =     5 ft + 3 ft + 1 .8 ft                        This has a large effect, as a lower pressure head
                                  =  9.8 ft                                       will also lower the flow rate and friction head.
                                                                                 Reduce the friction-head loss by using a larger
                  The system will require a pump with a capacity                  diameter supply manifold (two inches is a
               of 36 gallons per minute against 10 feet of head. It               practical maximum for residential systems).
               is always necessary to specify the total head when                Reduce the flow rate by using  smaller hole
               selecting a pump. The head and flow requirements                   size (1/8-inch is the minimum) - by increasing
               are checked against the performance curve pro-                     hole spacing.
               vided by the pump manufacturer. Examples of                       Raise the pump by placing more blocks under-
               performance curves are shown in Figure 5. It is                    neath it.
               important to use the performance curve for the                  A combination of choices can be made. The goal
               specific brand and size of pump to be used.                     is to design a system that works properly for the
               Performance curves vary among brands.                           lowest possible price. A larger pump is an easy
                    Step 3. Select a pump of proper capacity.                  solution, but will be more expensive than one of
                    Consult the appropriate performance curve.                 the other options. For most residential systems a
                    The system requirements of flow and total                  0.3- to 0.4-horsepower pump will be adequate
                    head (36 gallons per minute at 10 feet)                    with judicious selection of the other parameters.




                                Z4

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                                  4


                                                 CAPACITY GALLONS PER MINUTE                            
                                                      


                                                   THIS POINT FALLS BELOW THE CURVE; THEREFORE,
                                                   THE 4/10 HP. MODEL IS ADEQUATE


               Figure 4. Comparing pumping, requirements to performance curves


               10
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                                                N.
                                                           N.                                               Pulp 3, a. 4 @P

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                Figure 5. Examples of performance curves (capacity vs total head) ior tour submersible eifluent pumps




                Dosing volume                                                         Example:
                  Dosing volume is the amount of effluent pumped                      For a 900-gal pumping tank, 4-ft liquid depth
                to the absorption field each time the pump runs.                      (bottom of tank to outlet tee); 1 80-gal dose:
                The dosing volume must be large enough to                             Dosing depth = 0 80 gal/900 gal) x 4 ft
                provide adequate distribution in the field and                                         = 0.8 ft = 9.6 in.
                adequate resting time between doses, yet small                     The float control switch for the pump should be
                enough to avoid overloading. The minimum dose
                to provide adequate distribution depends on the                  set for a 10-inch drawdown to provide automatic
                size of the supply and lateral network.                          doses of 180 gallons.
                    Step 1. Calculate minimum dosing volume.
                    V dose = V supply + 5 (V laterals)                           Check-valve calculation
                    The minimum volume is the sum of the                           Any effluent which remains in the supply and
                    supply-line volume and five times the volume                 lateral lines of a properly sited system will drain
                    of the lateral lines. The volume of the lines is             back to the pumping chamber when the pump
                    calculated using Table 4.                                    shuts off. If this volume is too large, it can cause
                                                                                 overuse of the pump and excessive consumption
                                                                                 of electricity. A check valve may be needed to
                Table 4. Storage capacity per      100ft of PCV pipe             prevent this return flow to the pumping chamber,
                                                                                 especially on a large system with a long pumping
                                                 Storage Capacity                distance. Check valves should be avoided if
                Pipe Diameter             160 psi             Schedule 40        possible because they may malfunction when
                                                                                 used for septic tank effluent. In general, a check
                       in.                           gall 7 00 ft                valve should only be used if the total storage
                       1                      5.8                    4.1         volume of the pipes is greater than one fourth of
                       I 11@                 9.0                     6.4         the total daily waste flow.
                       1 '/2                12.5                     9.2
                       2                    19.4                    16.2              Step 1. Calculate storage volume.
                       3                    42.0                    36.7              V storage = V supply + V laterals
                                                                                      Example:
                                                                                      V storage = 13.6 gal + 32.4 gal
                    Example:                                                                     = 46.0 gal
                    1. Supply line      70 ft of 2-in. pipe
                       V supply = (701100) x 19.4 gal                                 Step 2. Compare to 1/4 daily waste flow.
                                  = 13.6 gal                                          Example:
                    2. Lateral lines = 360 ft of 11/4-in. pipe
                       V lateral =    (360/100) x 9.0 gal                             450gpdxl/4= 112 gal
                                   =  3 2.4 gal                                       46.0 gal < 112 gal
                    3. V dosing =     13.6 gal + 5 (3 2.4 gal)                        No check valve needed.
                                   =  176 gal

                  Dosing two to       four times per day provides
                adequate resting      time. For a 450 gallon-per-clay
                design, this would bearangeof 112 to225 gallons
                per dose (gal/dose).
                    Step 2. Select dosing volume.
                    Example:
                    Selecting 180 gal/dose would give between
                    two and three doses per day. This volume is
                    larger than the minimum in Step 1. If water
                    use is less than 450 gpd, dosing will occur less
                    frequently, providing longer resting periods
                    between doses.
                    Step 3. Compute the depth of effluent pumped
                    per dose. In order to set the pump controls to
                    deliver the proper dose, the depth of effluent
                    to be pumped from the tank for each dose
                    must be calculated. The computation is done
                    using the following equation: Dosing depth
                    (V close/V tank) x liquid depth of tank.

              12





                 CHAPTER 5
                 Equipment Spe--cifications




                  All necessary equipment and tools should be                  lid. Standard well tiles can be used for the risers,
                 clearly listed so they can be obtained prior to               provided that the inside diameter is larger than
                 building an LPP. To prepare this list, first consolidate      the access hole in the tank. All joints must be
                 the design specifications onto a single worksheet             sealed to prevent the infiltration of surface runoff
                 (Appendix 1). A copy of this worksheet alongwith              and groundwater to the tanks.
                 an accurate sketch including drainage and land-               Pipe and fittings
                 scaping requirements (Figure 3) should be filed
                 for every system which is installed. Using this                 All pipes and fittings in an LPP system should be
                 sheet, prepare a list of materials (Appendix 2). Be           made of PVC plastic. PVC is lightweight, easy to
                 sure that the materials meet the requirements                 use and resists corrosion. Alljoints must be sealed
                 discussed below. A sketch of the distribution                 with an appropriate PVC-solvent cement. The
                 lines (Figure 6) and the pump system (Figure 7)               supply manifold from the pumping chamber to
                 are useful for counting the fittings.                         the LPP distribution field is usually 11/2-inch or
                                                                               t,,inch PVC, depending on specifications of the
                 Septic tank and pumping chamber                               system (Chapter 4). A bushing or reducer may be
                  As noted earlier, an LPP system has two separate             needed to adapt the pump to the supply manifold.
                 tanks-a septic tank and a pumping chamber. If a               There should always be a threaded PVC union
                 conventional septic system is being replaced by               above the pump to allow easy removal or replace-
                 an LPP, the existing septic tank can be used (after           ment. Lateral lines are usually made of 11/4-inch
                 being pumped out), and only one additional tank               PVC. Appropriate holes in the laterals are drilled
                 installed.                                                    on site (Chapter 6).
                  The septic tank receives wastewater directly                   PVC pipe may be of thin-wall (160 psi) or
                 from the house. It is sized according to state and            Schedule 40 specifications, but must be of the
                 local regulations for conventional systems. (10               straight length variety. Thin-wall (160 psi) PVC is
                 NCAC I OA .1907). The septic tank must be of                  usually cheaper than Schedule 40. A globe or gate
                 two-compartment design for maximum solids                     valve for final pressure adjustment is installed in
                 retention. It is very important that the septic tank          the supply manifold inside the pumping chamber.
                 and pumping chamber are watertight. One-piece                 The valve should be made of PVC or bronze,
                 tanks are best. When using two-piece tanks, the               whichever is cheaper. All other tees, elbows, caps
                 tongue-in-groove joint must be carefully sealed               and reducers in the distribution system should be
                 with asphalt rope mastic.                                     made of PVC. The end of each lateral line is
                  Effluent from the two-compartment septic tank                equipped with a capped "turn-up" that provides
                 flows by gravity through a four-inch solid PVC                aboveground access for clean-out or back-flushing
                 pipe to the pumping chamber. The pumping                      (Figure 5). Using 45-clegree elbows rather than
                 chamber should have a liquid capacity of at least             90-clegree elbows for the turn-ups will make
                 two times the daily wasteflow from the house,                 clean-out easier to do. Galvanized caps may be
                 and can be a single-compartment design.                       used if PVC is not available.
                  Both the septic tank and pumping chamber                       In the few instances where a check valve is
                 must be provided with aboveground concrete or                 necessary (Chapter 4), it should also be installed
                 masonry (or their equivalent) manhole risers        ' to      with threaded fittings in the pump chamber to
                 provide easy access for clean-out and pump                    provide easy access for maintenance.
                 service. The riser should be placed over the                  Pump, float controls and alarm system
                 primary chamberof the septic tankand above the
                 pump access hole in the pumping chamber.                        A good-quality, submersible effluent pump
                 Risers should be wide enough to accommodate                   must be used in LPP systems. An expensive
                 the existing lids on the tanks, should extend at              grinder pump is not required because the septic
                 least six inches above the finished grade of the              tank effluent will be relatively free of solid material.
                 site and should also be covered with a concrete               A septic-tank effluent pump or a submersible,

                                                                                                                                    13











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               Figure 6. Details of distribution system                                                                       R4' -,tjl!@
              14












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                 Figure 7.De ails o fpurnping chamber





             sump pump that will not be corroded by sewage                 are two basic requirements for an alarm system:
             should be used in the pumping chamber. Pumps                  a  It must operate on a separate electrical circuit
             with built-in switches should be avoided, unless                 from the pump.
             the switch can be adjusted for the quantity of                9  It must activate a labeled and easily visible (or
             water to be pumped. The selection of pump size                   audible) signal in the home whenever the water
             is discussed in Chapter 4. Pumps in the range of 1/4             exceeds the normal "pump-on" level in the
             horsepower to 4/10 horsepower generally provide                  tank.
             sufficient capacity for residential LPP systems, but
             the pumping requirements for each system must                 Gravel
             be checked against the performance curve of the                  LPP systems require about six inches of gravel
             pump to be used. It is better to use a slightly larger        in the lateral distribution trenches. Gravel size
             pump than necessary, because the final pressure               should be from 3/8 inch to one inch. Pea gravel or
             can be adjusted with the in-line gate or globe                crushed rock may be used, but it must be washed.
             valve.                                                        Gravel placement is discussed in Chapter 6.
                The controls for the pumping system include a
             switching control for turning the pump on and off
             and a high-wateralarm to signal pump malfunctions             Home water-saving devices
             (Figure 6). The pump control system must be                      Any home with an LPP system must be equipped
             adjustable to meet the recommended loading                    with I, v-flow showerheads (three gallons per
             rates for different sizes and shapes of pumping               minut     and low-flush commodes (31/2 gallons or
             chambers. The controls must also be sealed against            less per flush) in order to minimize the hydraulic
             entry of corrosive and explosive gases from the               load on   the system. Those devices are a simple,
             effluent and should have N EMA (National Electri-             low-cost way of reducing water consumption
             cal Manufacturing Association) approval.                      with no inconvenience to the homeowner. They
                The two types of switches which have proven                are required by the North Carolina Building Code
             the most useful are magnetic, level-control switches          in all new construction. Low-flow showerheads
             and sealed, mercury switches. The magnetic                    and retro-fit dams for commode tanks should be
             level control consists of two floats suspended                used in any existing home where an LPP is
             from a sealed, magnetic switch. This switch has               installed.
             been reliable and the pumping volume is easily
             adjusted. Mercury switches are activated by a
             sealed float which contains a tube of mercury in
             contact with power leads. Best performance has
             been obtained using two switches-one to close
             the pump circuit and the other to open it.
             Automatic timers with backup mercury floats
             have been successful in a few systems where
             uniform timing of the doses was important. Dia-
             phragm and some mechanical float switches
             have not been acceptable for LPP use. The range
             of adjUstment is often inadequate and the switches
             do not provide good service in a sewage environ-
             ment.
                In addition to the on and off control floats,
             there must beaseparate float control forthehigh-
             water alarm. This may be a sealed, mercury-float
             switch mounted several inches above the on
             float. The high-water alarm should consist of a
             light bulb and/or audible signal mounted over a
             sign marked "wastewater system alarm" in a
             visible place in the home. such as the kitchen or
             utility room. It should be on a separate electrical
             circuit from the pump power line, and be equipped
             with a test switch. The alarm is activated if the
             water level in the pumping tank rises above the
             "pump-on" float control. The tank provides at
             least one day or more of excess storage capacity
             (depending on water use in the home) during
             which time the system must be repaired. Refer to
             Chapter 9 for repair and maintenance tips.
                Complete control boxes for high-water alarms are
             available commercially. Simpler and cheaper sys-
             tems can be assembled by an electrician. There

             16





                  CHAPTER 6
                  Installation Pro.cedures




                     The actual installation of an LPP is simple and             chamber. This can be done with grassy swales,
                  straightforward, and can usually be accomplished               open ditches or curtain drains.
                  by three or four people in one day.                               If the site requires imported fill to improve
                                                                                 surface drainage, it must be incorporated evenly
                  Tools and supplies                                             into the underlying natural soil. It is very important
                                                                                 that no sharp interface remain between the natur-
                     A backhoe is needed only for installation of the            al and imported soil layers. Before applying the
                  two tanks. All other excavation is done with a                 imported fill to the absorption area, the ground
                  small trenching machine that will excavate a cut               surface must be tilled with a small plow or
                  four to six inches wide. A transit or similar instru-          cultivator. Fill should be applied with a minimum
                  ment is necessary for staking out the lateral lines            of wheeled traffic on the area, and the area tilled
                  on sloping lots. Other tools needed for installation           again to ensure even mixing. A very small tractor
                  are*                                                           should be used to spread the material around and
                  ï¿½  Shovels, wheel barrows- for moving gravel                   to provide a convex shape to the area. There
                  ï¿½  Electric drill (with power pack or generator, if            should be no low spots or depressions, and the
                     necessary)-for drilling holes in lateral lines              final shape should shed, rather than accumulate
                  *  Drill bits                                                  rainwater. Use of fill to supplement the soil
                  ï¿½  Hack saw, extra blades-for cutting PVC pipe                 profile is discussed in Chapter 8.
                     to required lengths                                            After the area has been cleared and shaped, the
                  ï¿½  PVC glue (and rags)                                         location of the lateral lines and supply manifold
                  ï¿½  Mortar-to seal tank openings                                should be accurately staked out according to
                  ï¿½  Measuring tape                                              design specifications. Each lateral line must be
                  ï¿½  Electrical wiring tools                                     laid out along a level contour using a transit. One
                     in addition to tools, a complete list of parts and          lateral may be higher or lower than the next one,
                  materials should be compiled from a sketch of the              but each individual lateral must be level. In no case
                  system (See Appendices 2 and 3).                               should a lateral line be allowed to slope away from
                  Site preparation and imported fill                             the manifold.
                     One of the most important concerns for an LPP               Tank installation.
                  system is to protect the site from soil disturbance               The two-compartment septic tank is installed in
                  by heavy equipment. Removal or compaction of                   the same way as a conventional system. Waste-
                  the topsoil, especially during wet weather, may                water from the house flows directly into the large
                  destroy the site's suitability for an LPP. As soon as the      compartment of the tank. The pumping chamber
                  absorption area has been designated, it should be              is installed next to the septic tank, but its direction
                  flagged, roped off and "quarantined" from con-                 must be reversed so that the tee end become@- the
                  struction traffic. No site preparation or LPP con-             inlet end adjacent to the septic tank. The lo%%er
                  struction work should occur if the soil is wet. As a           invert of the tee end ensures proper gravity floA
                  rule of thumb, if the soil is too wet to plow, it is too       from the septic-tank outlet into the pumping
                  wet to disturb for system construction.                        chamber. The tanks are connected with an appro-
                     After the location is staked out and the soil is            priate length of solid, four-inch PVC pipe. I ri!t-t
                  dry enough to plow, the site should be cleared of              and outlet openings around the pipe must then
                  brush and small trees. If larger trees are removed,            be sealed with mortar.
                  they should be cut off rather than up,rooted in                   The tank access lids must be equipped .%lth
                  order to avoid creating depressions and damaging               water-tight masonry or concrete risers to at least
                  the soil-pore network.                                         six inches above grade. These provide easy accc-@,
                     Provisions must be made for intercepting or di-             for repair and inspection, and help keep su rta( e
                  verting surface waterand shallow groundwateraway               water out of the tanks.
                  from the absorption area, septic tank and pumping                 If an LPP is being installed to replace an existing

                                                                                                                                         17





             conventional septic system, only one additional               only drilled through one side of the pipe. If the
             tank (the pump chamber) must be installed.                    drill bit should go through both sides, or if a hole is
             However, the existing septictank must be pumped               drilled in the wrong place, it can be sealed by
             out before installing the LPP.                                wrapping with duct tape. Lateral pipes are placed
                                                                           holes-down in the tren ches. A short tu rn- u p with a
             Supply Manifold                                               capped end is at the end of each lateral (Figure 8).
                The supply manifold conveys effluent from the              The capped end must be brought up above or
             pump to the distribution laterals. Any effluent               flush with the final grade. As the trench is backfilled,
             remaining in the lateral lines when the pump                  the turn-up may be placed inside a short length of
             shuts off should drain back to the pumping                    four- or six-inch PVC or terra cotta pipe to protect
             chamber through the supply manifold (unless the               it from lawn mower damage, while still providing
             system is large enough to require a check valve).             easy access. When installing each lateral, care
                                                                           must be taken to ensure that the holes are down
             The manifold joins each lateral through a short               and the turn-up pointed upward before the quick-
             riser pipe connecting a reducing tee on the mani-             drying PVC glue hardens. Positioning of the lateral
             fold to a 11/4-inch elbow or tee on the lateral               should be checked to make sure it is level in the
             (Figure 6). This assembly places each lateral pipe            trench.
             about six inches higher than the supply manifold                After the lateral lines are in place and leveled,
             and helps prevent the back-flow of effluent from              they are covered with another two to four inches
             a higher lateral to a lower lateral. The individual           of gravel. The earthen dams in the lateral trenches
             riser units may be assembled earlier and glued in             and near the manifold must be tightly tamped
             place between the laterals after the manifold is cut          from the trench bottom to the ground surface.
             into segments. Because the lateral line is now                Finally, the trenches are backfilled with topsoil.
             several inches higherthan the manifold, the mani-             Turn-ups should then be cut to appropriate lengths,
             fold requires a trench six inches deeper than the             fitted with caps and (if desired) protected with
             laterals. In the special case of pumping downhill,            short segments of four- or six-inch PVC or terra
             the laterals are placed lower than the manifold               cotta.
             (See Chapter 7).
                After the supply manifold has been placed in its           Pump and controls
             trench and lateral lines connected, it should be                Details of pump installation are show in Figure
             backfilled with tightly tamped soil. The supply-              7. The pump must be placed on two concrete
             manifold trench must not be backfilled with                   blocks set next to each other on the bottom of the
             gravel, or the trench may become a conduit for                tank. This prevents the pumping of any solid
             clownslope flow of effluent from the laterals. The            particles which can clog the LPP system. A piece
             outlet hole in the pumping tank should not be                 of nylon rope or other non-corrodible material
             sealed with mortar until after the pu'mp is in place.         should be attached to the pump and to the outlet
             Lateral lines                                                 pipe for lifting the pump in and out of the
                                                                           chamber. (The PVC outlet pipe is too fragile to
                The lateral trenches are usually cut 18 inches             support the pump).
             deep. Some soil profiles will require shallower                 Controls are fastened to the outlet pipe with
             placement. The depth of a given lateral trench                clamps or brackets supplied by the manufacturer.
             should be uniform from the manifold to the end                The lower level control or "pump-off" must be
             of the lateral. In nocase shouldthetrench bottom              positioned above the pump, so that the pump
             be,allowed to slope away from the manifold. The               remains submerged at all times. The upper level
             lateral trench must not extend more than one or               control "pump-on" is positioned to pump a speci-
             two feet beyond the end of the lateral pipe. Small            fied volume of effluent (Chapter 4). The high-
             earthen dams are placed at the beginning of each              water control float is then mounted about three
             lateral trench, and at 20-foot intervals thereafter,          inches above the upper pump-on control. (Note:
             to help maintain uniform distribution of effluent             Care must be taken to ensure that the floats do
             along each trench. The dams can be tamped into                not become fouled by other components in the
             place or left uncut from the soil (Figure 8). Lateral         tank such as the electric power cord or the lifting
             trench bottoms are then lined with three to six               rope.)
             inches of gravel (remember to put no gravel in the              The pump outlet pipe should be connected to
             supply manifold trench).                                      the supply manifold with a threaded PVC union to
                The 11/4-inch PVC pipes should be laid out and             allow quick removal. The gate or globe valve must
             cut to proper lengths for the lateral lines. Holes            also be installed in the supply line (within the
             are drilled (in a straight line) according to the             pump chamber) to allow final adjustment of the
             design specifications after the laterals have been            pressure. If effluent will be pumped downhill, a
             cut to their proper length. The first hole in each            1/4-inch siphon-breaker hole must be drilled in the
             lateral should be drilled two to three feet from the          bottom of the supply line before it leaves the
             manifold; the last hole should be drilled two to              pump tank. This breaks any vacuum in the system
             three feet from the end of the lateral. Holes must            and prevents the inadvertent siphoning of effluent
             not coincide with the earthen dams. Holes are                 out of the tank. This hole is very important.

             18






                   Power and control cords should be guided out               All electrical connections must be made outside
                 of the pump chamber through a recessed channel             the pumping chamber. Power cords from the
                 oropening thatwill protect the cords from damage           pump and controls should be plugged into a
                 by the concrete lid.                                       NEMA-approved outdoor receptacle mounted
                                                                            outside of the pumping chamber. The receptacle
                 Electrical connections                                     must not be located inside the pumping chamber
                   As noted earlier, the pump and high-water                due to the corrosive and explosive gases that may
                 alarm must be placed on separate electrical circuits.      form from the sewage.
                 (if the pump circuit fails, the alarm must still be          Electrical connections may be made inside the
                 able to operate). Follow the manufacturer's recom-         pumping tank only if wired inside a sealed, water-
                 mendations for proper fuses or circuit- breakers.          tight box. Some level-control switches have such a

















                                           V su,   lsLr_-
















                                                        SA_'4r-ILL_---T2    SOIL
                                                                                                               -WIRQ. J9







                                                                                     //E




                                                                          SOIL)





                 Figure 8. Details of absorption trenches



                                                                                                                             I n






                box built into the housing but are more expensive
                than the plug-in devices.
                Wiring between the pumping chamber and the
                house should meet state and local code require-
                ments. A lightning arrestor is recommended to
                protect the pump and controls from electri6l
                surges.
                Proper operation check
                .After all components have been installed and
                connected, the system should be checked for
                proper operation. With electrical power turned
                off, fill the pumping chamber with a garden hose
                (or allow effluent to accumulate) until the liquid
                rises to the level of the high-water alarm float.
                Turn on the electrical power. The alarm light
                should go on in the house, and the pump should
                start operating. The alarm light should go off when
                the liquid level falls below the high-water float.
                The pump should turn off when the liquid reaches
                the lowest float control. Be sure the pump is still
                completely submerged.
                Pressure head adjustment
                The pressure head must be adjusted to match
                that specified in the design. The pressure head is
                measured as the height liquid will rise above the
                turn-up elbow when the pump is running. To
                adjust the head:
                ï¿½Glue a four-foot length of pipe (preferably                                                                                   4
                clear) to a threaded adapter that will screw
                onto the turn-up adapters.
                ï¿½Replace the turn-up cap with the pipe and
                adapter.
                ï¿½Turn the power on to allow liquid to rise in the
                pipe.
                ï¿½ Adjust the gate or globe valve in the pumping
                tank until the effluent reaches the desired
                height in the pipe. Remember to include the
                distance belowthe ground surfacetothe lateral
                line wl@ i measuring the height.
                Final landscaping
                After the LPP is installed, the following should
                be checked to ensure that the system will not be
                overloaded with excess rainwater and runoff:
                ï¿½The distribution field is shaped to shed rain-
                water and is free of low areas.
                ï¿½Curtain drains, grassy swales or ditches for
                divertingground and surfacewaterare properly
                installed.
                ï¿½Gutter and downspout drains are directed away
                from the system.
                Any problems should be corrected before approv-
                ing the system.
                Finally, the entire area should be planted with
                grass in order to prevent erosion. The soil should
                be properly tilled, limed (if necessary) and fertilized
                before planting. After applying an appropriate
                grass seed, the area should be heavily mulched
                with straw or other suitable material.


                20





                 CHAPTER 7.
                 LPP Design and Installation on
                 Sloping Ground'


                    A sloping site presents a special set of problems                   elevation head in order to achieve uniform distri-
                 for LPP design. The system must be carefully                           bution. The load on each line must be individually
                 planned to obtain even distribution of effluent                        calculated. All the loads are then balanced by
                 throughout the absorption area. The pressure                           modifying the design of individual lines where
                 head on each line is different due to a different                      needed.
                 elevation. Each foot of elevation difference changes                     Determine dosing rate:
                 the pressure head by one foot. Also, perched                               Step 1. Measure and record the elevation of
                 water moving downslope onto the system and                                 each line. Make sure that each line is laid out
                 effluent moving from the upper trenches to the                             on the contour (see example below for sum-
                 lower trenches can cause overloading. Pumping                              mary of steps).
                 uphill or downhill to the absorption field can                             Step 2. Round-of'f each elevation to the near-
                 create additional problems. This chapter highlights                        e5t half-foot.
                 changes inthedesign procedure which are neces-                             Step 3. Compute the difference in elevation
                 sary when designing LPP sy          .stems on slopes.                      of each line from the highest line.
                 Layout                                                                     Step 4. Determine the pressure Kead on each
                    The procedure is similar to that in Chapter 3,                          line. First select the pressure head for the
                 with careful emphasis placed on the following                              highest line. Then add the elevation difference
                 points:                                                                    (Step 3) to determine the pressure head on
                 ï¿½  Lateral trenches must be placed on contour                              the lower lines.
                    and earthen dams installed as needed to ensure                          Example:
                    even distribution of effluent in each trench
                    (Figure 9).                                                             Calculate the pressure head on each line for a
                 ï¿½ The effects of slope can be lessened by making                           system with five 60-ft lines with elevations
                    systems as long and narrow as possible across                           shown below. Pressure head for the highest
                    the contour (Figure 2C, page 6). This design                            line is 2 ft. See Table 5 below.
                    uses fewer and longer lines, decreasing the
                    elevation difference between the highest and
                    lowest lines.
                 ï¿½  Systems with more than four feet of elevation                       Table 5. Calculating pressure head
                    difference between the highest and lowest                                                                                 Pressure
                    laterals cannot be designed with a single mani-                                 Elevation Round Off Difference              Head
                    fold. Separate manifolds for the upper and                            Line       (Step 1)      (Step 2)     (Step 3)      (Step 4)
                    lower lines must be used (Figure 9b). Each
                    manifold must have its own pressure-control                                                          - ft
                    valve (gate or globe) for pressure adjustment.                      IHighest      3 59.2        359               0         2
                 ï¿½  Interceptor or curtain drains are often necessary                   1             3 58.6        358.5             0.5       2.3
                    to divert water moving from uphill.                                 3             338.2         358               1         3
                 ï¿½ When it is necessary to pump downhill, dis-                          4             35'1.9        358               1         3
                    tribution lines should be in deeper trenches
                    than the supply manifold. The opposite is true                      5Lu,...st     351.0         357               2         4
                    for level or uphill Systems (Figure 10).
                 ï¿½ Installation on slopes greater than 30 percent
                    is not recommended unless installation is to be                      The pressure head should not exceed five feet
                    done entirely by hand.                                              on any of the lines. If it does, several modifications
                                                                                        can be made. If suitable space is available, redesign
                 Dosing and distribution                                                the system, making it longer and narrower, thus
                    The design must compensate for differences in                       covering less of a range in elevation. Remember

                                                                                                                                                   21






                that the lateral length is restricted to 70 feet or                flow to lower lines can be reduced by increas-
                less and the spacing to five feet or more.                         ing the hole spacing to greater than five feetor
                 A; another option, lower the selected pressure                    reducingthehole sizetoassmallas 3/32 inch.
                head on the highest line and recalculate the                       But these sizes and spacings must not be used
                heads on the remaining lines. The head on the                      for an entire system.
                highest line should be no less than one foot and;s
                best kept at two feet.                                             Example:
                 Finally you can split the line into two or more                   For the system in discussion, change the hole
                manifolds. This is discussed in detail later in this               spacing to 4 ft in line 1 (highest) and to 6 ft in
                chapter.                                                           line 5 (lowest).     -
                   Step 5. Check to see if the pressure head                       See Table 7 below.
                   exceeds five feet on any lines.
                   Example:                                                    Table 7. Balancing the flow rate among lines
                   Highest pressure head is 4 ft, therefore no
                   modifications need to be made.                                        Hole      No. of
                                                                               Line    Spacing      Holes     Flow/Hole Flow/Line*
                   Step 6. Determine the flow rate per hole for                           ft                  _gPM -
                   each line using Table 2 (pg 8) and the
                   pressure heads calculated above. (See follow-               1          4          15          .41           6.2
                   ing example.)                                               2          4.5        13          .46           6.0
                                                                               3,4        5          12          .50           6.0
                   Step 7. Determine the flow rate for each line.              5          6          10          .58           5.8
                   Example:                                                    *For svstems with lines of variable length, the flow rate/ft is
                   Using the pressure heads above and assuminga                compared as described in Step 7.
                   5-ft hole spacing on 60-ft lines (12 holes/line),
                   prepare Table 6 below.                                       When changing hole size or spacing to balance
                                                                               the flow it is very important to make the changes
                                                                               and instructions simple and clear. Hole placement
                Table 6. Flow rate for each line                               and line installation should be inspected to ensure
                     Pressure Head Flow Rate/Hole       Flow Rate/Line         that they are done properly.
                Line    (Step 4)         (Step 6)           (Step 7)               Step 9. Calculate total dosing rate. The dosing
                -                                                                  rates for each line are added to obtain the
                           ft             gpM                _qPM                  total.
                1          2              .41                4.9                   Example:
                2          2.5            .46                5.5
                3,4        3              .50                6.0                   For the system above:
                5          4              .58                7.0                   Dosing rate = 5.8 + 6.0 + 6.0 + 6.0 + 6.2 gpm
                                                                                                = 30.0 gpm
                                                                                   (Add 2 gpm if a siphon-breaker hole is needed.)
                 The dose to the lower lines is larger due to the
                @nc.-eased pressure head, while the dose to the                Pump selection
                -i'ooer lines is reduced, causing overloading of the            The pump is chosen in the same manner as in
                -,.,.,.er lines. The flow rate should be balanced to           Chapter 4. When pumping uphill the elevation
                VNriLhin 10 percent among lines on the same                    head increases. if the hill is large enough it may
                manifold. It is wise to reduce the flow even lower             become impractical to adjust the system for use
                in the lowest lines, because they receive an                   with a 4/1 0-horsepower pump. It may be neces-
                additional hydraulic load from downslope effluent              sary to use a larger, more expensive pump.
                movement from the upper lines.                                  If it is necessary to pump downhill, a 1/4-inch
                 Often the lengths of lateral lines vary. Some                 siphon-breaker hole must be drilled in the supply
                may be shorter than others to avoid obstacles                  line in the pumping tank (Figure 7) to avoid
                such as large trees, rocks or complex slopes.                  unintentional continuous siphoning of effluent
                When this is the case, the flow rates of the lines             from the tank to the absorp'tion field.
                cannot be directly compared. Rather the flow                    In some downhill systems, intentional siphoning
                rates per foot of line must be calculated and these            can be used instead of pumping to provide
                compared.                                                      distribution. A gravity-dosing siphon replaces the
                   Step 8. Balance flow rate among lines. This                 electric pump. Siphons of different sizes are
                   can be done either by changing the numberof                 available, and the siphon and dosing volume
                   holes or changing the size of the holes. The                must be matched. The remainder of the system

                22
















                  Zli4@1





















                                                                                                                                As U  O%J



















                a-S?Uj'l"l&WiPCLO LeCUT AJ 6OQOi;OIJR


               Figure 9. Layout of LPP systems on s/opes


                                                                                                                                          23







































                                        -FE J L7'


















                                7























                Figure 10. Manifold placement on slopes


                24





                  design is the same as when a pump is used.                          Follow the procedure of steps six through nine
                    The remaining steps in the design of LPP systems                in the previous section to balance the flow rates
                  for sloping ground are the same as that for level                 and determine dosing rates.
                  ground (Chapter 4).                                                 Pump selection is done as in Chapter 4. When
                                                                                    using a split manifold, the total friction loss de-
                  Design of split manifold. systems                                 creases while the pipe volume increases. In many
                    A split manifold system is used when the                        cases it may be best to decrease the diameter of
                  elevation difference between the lowest and                       the manifolds after they split. This will decrease
                  highest lines exceeds four feet. The supply line is               the pipe volume, and may avoid the need for a
                  split into two or more manifolds, each connected                  check valve.
                  to a subsystem of distribution laterals (Figure 9b).                For most systems the gate or globe valves
                  Each manifold is equipped with a gate or globe                    should be 11/4-inch diameter because they are
                  valve so the pressure heads on the *subsystems                    easier to adjust than larger valves. Reducing
                  can be adjusted separately. This allows each                      adapters will be needed to fit these valves into
                  subsystem to act as an independent system al-                     larger diameter manifolds.
                  though they may be operated from the same
                  pump. The following is an example of a design
                  where a split manifold is necessary.                              Table 9. Establishing a subsystem
                       Example:                                                                         Elevation and                  Pressure
                       Lines are to be laid out on contours at 1319.8,                                    Round Off      Difference     Head
                       1318.4,11317.0,11315.2, 1313.7 and 1312.4 ft.                Subsystem Line        (Steps 1,2)     (Step 3)    (Step 4)
                       Steps 1-5. The procedure in the previous                                                             ft
                       section is followed. The calculations are sum-                    1         1       1320               0          2
                       marized in the following example.                                           2       1318.5             1.5        3.5
                       Example:                                                                    3       1317               3          5
                       Pressure head of highest line is set at 2 ft. See                 2         4       1315               0          2
                       Table 8 below. The pressure head exceeds 5                                  5       1313.5             1.5        3.5
                       ft for 3 lines; therefore a split manifold will be                          6       1312.5             2.5        4.5
                       used.



                  Table 8. Calculating the pressure head

                                                                     Pressure
                          Elevation     Round Off Difference          Head
                  Line     (Step 1)       (Step 2)     (Step 3)      (Step 4)

                                                   ft

                    1      1319.8         1320            0            2
                    2      1318.4         1318.5          1.5          3.5
                    3      1317.0         1317            3            5
                    4      1315.2         1315            5            7
                    5      1313.7         1313.5          6.5          8.5
                    6      1312.4         1312.5          7.5          9.5


                       Step 6. Split the system into two subsystems.
                       Example:
                       Subsystem I (higher)          lines 1-3
                       Subsystem 2 (lower)          lines 4-6
                       Step 7. Repeat steps 1 through 5 indepen-
                       dently for each subsystem.
                       Example:
                       Set the pressure head at 2 ft for the highest
                       line of each subsystem. See Table 9 below.
                       No pressure head exceeds 5 ft; therefore this
                       system is satisfactory.

                                                                                                                                          25





            CHAPTER 8
            Modified LPP Systems Using Fill




              Most sites with a restrictive horizon or a season-           Step 3. Converi to cubic yards.
            ally high, water table within 24 inches of the                 Example:
            surface are not suitable for a standard LPP system.
            Many are not suitable for any soil-absorption,                 V fill = 2800 ftl/27 ft' per yd'
            waste-treatment system. But some of these sites                      = 104 yd  3
            can be used for waste treatment if the soil is
            supplemented with fill that has been carefully               The remaining design steps follow the procedure
            selected and added.                                        of Chapters 3 and 4.
              When there is 16 inches to 24 inches of usable
            soil on an acceptable site, a modified LPP can be          Installation
            installed. The soil must have suitable or provision-         The success of a modified LPP depends on the
            ally suitable texture, structure and permeability          care used in selecting and incorporating the fill
            (10 NCAC 10A .1920). After the addition of fill,           material. The fill must have a sandy loam or
            trenches are placed as shallowly as three inches           loamy sand texture. The fill should not be hauled
            to four inches into the natural soil. The design and       or worked wet.
            installation of the modified LPP are discussed               As v0th all LPP systems, the site must be
            below.                                                     protected from traffic. Prior to incorporating the
              When there is less than 16 inches of usable soil,        fill, brush and small trees should be removed and
            a mound system can be built, where the distribution        the soil suface loosened using a cultivator or
            lines are placed above the soil surface in imported        garden plow. It is very important that the soil be
            fill. The design and construction of mounds is             worked only when dry. Working damp or wet soil
            discussed in the manual, Design and Installation           can cause compaction and sealing, leading to
            ofMound Waste Treatment Systems published by               failure of the system.
            UNC Sea Grant.                                               Fill is moved to the system using a front-end
                                                                       loader, being careful to avoid driving on the
            Modified LPP design                                        plowed area. The first load of fill is pushed into
                                                                       place using a very small crawler tractor with a
              The only difference between designing a mod-             blade or a roto-tiller with a blade. The fill is then
            ified and standard LPP is the calculation of the fill      tilled into the first few inches of natural soil to
            .-cuirements. The volume of the fill needed is the         create a gradual boundary between the two.
            ,-a. to be filled multiplied by the depth of fill. The     Failure to do this could ruin the system by forming
              t@a to be filled is the absorption field plus a five-    a barrier to water movement at the soil-fill interface.
            ,jot buffer around the edges.                              Subsequent    loads of fill are placed on the system
                Step 1. Calculate area to be filled. Add 10 feet       and tilled, until the desired height is reached. The
                to the length and width of absorption area to          site should be shaped to shed water and be free
                allow for buffer space.                                of low spots before proceeding.
                                                                         To install the LPPfoilow the procedure discussed
                Example:                                               in Chapter 6.
                Fora 60ftx 30ft absorption field tobefilled 1
                ft deep:
                Total area = 70 ft x 40 ft

                Step 2. Calculate the volume of fill needed.

                Example:
                V fill @ total area x depth of fill
                V fill = 70 ft x 40 ft x 1 ft
                      = 2800   ft3

            26





                  CHAPTER 9
                  Inspection and Maintenance




                  The successful performance of an LPP relies on              solids at the ends of the lateral lines. These should
                  proper design and installation. The details for a           be removed at least once a year by unscrewing
                  given system, from site preparation to final land-          the caps on each of the turn-ups, and back-
                  scaping, should be carefully specified on the               flushing the laterals with a garden hose.
                  Improvements Permit. This helps clarify the re-               Pressure head in the upper and lower laterals
                  sponsibilities of the property owner, contractor            should also be checked and adjusted one month
                  and permitting agency and helps avoid last-minute           after installation and annually thereafter (Chapter
                  surprises when issuing a Certificate of Completion.         6). Proper pump and float-control operation
                  items on the Improvements Permit (and associated            should be checked during all routine inspections.
                  design specifications for the LPP system) should            If the alarm panel has a "push-to-test" button, it
                  be inspected by the permitting agency in four               should be checked regularly. Pump maintenance
                  stages as outlined in Appendix 4.                           should follow the manufacturers recommendations.
                  Installation inspection                                     Repair procedures
                  Regulatory agencies are strongly recommended                  The alarm light should go on whenever effluent
                  to withhold the Certificate of Completion until all         in the pump chamber rises above the pump-on
                  the above requirements are satisfied. A checklist           level control. This can occur for several reasons:
                  similar to Appendix 4 should be completed and               9 Power failure: If there has been a power failure,
                  filed each time a system is installed to ensure               effluent will continue to accumulate in the tank
                  completion of the requirements.                               until power is restored. At this time the alarm
                                                                                may come on for a brief period (less than 30
                  Operation inspections                                         minutes), but will go off as soon as the pump
                                                                                draws down the effluent.
                  A properly designed and installed LPP system                  Pump or switch failure: If the pump or level
                  requires very little maintenance. Several routine             controls malfunction, they can be quickly re-
                  items should be checked periodically and an                   placed by unscrewing the PVC union and lifting
                  extra pump should be readily available. LPP systems           the entire assembly out of the pumping chamber
                  should be observed by the regulatory agency one,              (use the nylon lift rope). Be sure to turn off the
                  three, six and nine months after initial installation,        power supply, and disconnect all cords before
                  and every six months thereafter. An inspection                removing or replacing the pump or control
                  report should be completed and filed each time                assembly.
                  the system is checked. A sample format is shown             9 Clogged valve or discharge holes: If the distri-
                  in Appendix 5.                                                bution system becomes clogged, the tank will
                                                                                not be emptied. Back-flush the laterals and
                  Routine maintenance                                           supply manifold if necessary.
                                                                                Before replacing any components, make sure
                  All septic tanks, whether for conventional or               that the level controls have not simply become
                  alternative systems, require occasional pumping.            tangled. The problem can usually be isolated b@,
                  Sludge and scum accumulation should be checked              checking the pump operation independently from
                  annually. Virtually all solids will be retained in the      the controls. Repair or replace the approprii:e
                  first compartment of the two-compartment septic             components.
                  tank. Little or no accumulation should occur in
                  either the second compartment of the septic tank
                  or in the pumping chamber. The rate of sludge
                  a
                  c
                  umu
                  c    lation will vary with individual living habits.
                  Most septic tanks require pumping about once
                  every four years.
                  Some LPP systems may gradually accumulate

                                                                                                                                   27





               Appendix 1. Design specifications for example LPP (Chapters 3 and 4)
               File a copy of this sheet along with an accurate sketch for each LPP designed.
                                     Daily waste flow                                          450 gal
                                     Septic tank size                                          1200 gal
                                     Pumping tank size                                         900 gal
                                     Effluent loading rate                                     0.25 gal/ftl/day
                                     Absorption area                                           1800 ft'
                                     Total length of laterals                                  360 ft
                                     Lateral diameter                                          11/4 in.
                                     Lateral configuration                                     6 x 60 ft lines
                                     Supply line length                                        70 ft
                                     Supply line diameter                                      2 in.
                                     Manifold placement                                        side
                                     Hole size*                                                5/32 in.
                                     Hole spacing                                              5 ft
                                     Number of holes                                           72
                                     Pressure head                                             3 ft
                                     Flow per hole                                             0.50 gpm
                                     Total flow                                                36 gpm
                                     Elevation head                                            5 ft
                                     Friction head                                             1.8 ft
                                     Pressure head                                             3 ft
                                     Total head                                                9.8 ft
                                     Pump requirements                                         36 gpm, 9.8 ft of head
                                     Storage volume in laterals                                32.4 gal
                                     Storage volume in supply line                             13.6 gal
                                     Total storage volume                                      46.0 gal
                                     Dosing volume                                             180 gal
                                     Dosing depth                                              10 in.
                                     Check valve needed?                                       No

                    on hole size, spacing, pressure head and flow must be listed ioreach I ine for systems where lines are different (such as sloping lots).






















            28





                    Appendix 2. Pipe and fittings for example LPP (Chapters 3 and 4)
                            Type                          Size                 Quantity                                  Description
                    Pipe,   160 psi                 4 in.                           .10 ft             Connects septic tank to pumping tank
                    Pipe,   160 psi                 2 in.                           70 ft              Supply manifold
                    Pipe,   160 psi                 11/2 in.                        10 ft              Connects pump to supply manifold
                    Pipe,   160 psi                 11/4  in.                       380 ft             Laterals plus extra length for turn-ups
                    Tee*                            2 x 2 x   11/4 in.                 5               For joining manifold to first 5 laterals
                    Elbow                           2 x 11/4   in.                     I               For joining manifold to last lateral
                    Elbow                           11/4  in.                          12              6 for joining laterals to manifold
                                                                                                       6 for turn-ups
                    Male adapter                    11/4  in.                          6               For turn-ups
                    Threaded cap                    11/4  in.                          6               For turn-ups
                    Male adapter"                   11/2  in.                          3               1 for pump outlet
                                                                                                       2 for gate valve
                    Elbow                           11/2  in.                          1               For pump to supply line connection
                    Bushing                         11/2  x 2 in.                      1               For pump to supply line connection
                    Threaded union                  11/2  in.                          1               For quick removal of pump
                    Gate valve                      11/2  in.                          1               PVC or brass
                    PVC glue                        1 qt                               1
                    PVC primer                      I qt                               1

                    *Details of these connections are shown in Figures 5 and 6.
                    -Size of this adapter and the following fittings depend on size of pump outlet.



                    Appendix 3. Other supplies for example LPP
                            Type                        Size                Quantity                                      Description
                    Pump                            0.4 hp                          I              Submersible effluent pump
                    Switch                                                          1              Sealed level controls adjustable to 10 in.
                                                                                                   drawdown
                    Alarm                                                           1              Sealed mercury float switch and alarm light
                    Wiring                                                                         Approved outdoor receptacle, wire and conduit
                                                                                                   for 11 OV service
                    Septic Tank                     1200 gal                        1              Two compartment
                    Pumping Tank                    900 gal                         1              Single-compartment septic tank
                    Risers                                                          2              Concrete risers or well tiles, or blocks and
                                                                                                   mortar-to raise tank lids six in. above final
                                                                                                   grade
                    Lids                                                            2              To fit on risers
                    Gravel                          1/8-1 in.               5 ycls.                Washed
                    Concrete blocks                                                 2              Raised support for pump
                    Nylon rope                                              8 ft                   To remove pump from tank
                    Mortar                                                                         To seal around suppl@'Iine and riser
                    Grass seed                                                                     If needed to establish grass cover
                    Lime
                    Fertilizer
                    Mulch



                                                                                                                                                                 29






             Appendix 4. LPP Construction Inspection Checklist
             Site Identification

             Site Preparation                                                 Date
             1. Is the site in the right location?
             2. Roped off and protected from traffic?
             3. Small trees and brush cleared?
             4. Provisions for site drainage?
             5. Fill incorporated with underlying soil?
             6. Distribution field shaped to shed water?
             7. Lines staked out properly?
             8. Comments



             Construction Check                                              Date

             1. Tanks:
                Proper size and type?
                Installed properly?
             2. Manifold and laterals:
                Depth of gravel suitable?
                Placement of dams?
                Holes drilled properly and placed downward?
                Manifold and laterals connected properly?
             3. Water conservation devices installed in house?
             4. Comments




             Operation Check                                                 Date
             1. Pump and switches operating?
             2. High water alarm operating?
             3. Electric receptacle outside pump tank?
             4. Pressure head in lateral lines?
               a. Lowest
               b. Highest
             5. Comments




             Final Landscaping                                              Date
             1. Site shaped to shed rainwater?
             2. Any low areas?
             3. Diversion drains?
             4. Downspout drains directed away from system?
             5. Seeded and mulched?
             6. Comments



            30






               Appendix 5. Maintenance Checklist
               Site Identification                                                Date
               System Type

               Site Examination
               1. Any rainfall in last 3 days?
               2. Effluent poncled on surface?
               3. Indications of recent ponding?
               4. Ground above system damp and mushy
                  compared to surrounding area?
               5. Noticeable odor of sewage?
               6. Other



               If any "Yes" answers, sketch location and extent on back of page.
               Site Maintenance

               1. Condition of vegetable cover
               2. Site drainage (roof water, ditches, etc.)
               3. Riser and lid
               4. Turn-ups
               5. Erosion

               Pump Examination
               1. Pump and switch properly plugged in?
               2. Pump operating?
               3. Switch operating?
               4. Good seal where supply line leaves tank?
               5. Quality of effluent
                   Greasy?
                   Sludge accumulation?
               6. Measure pressure head and adjust.
                   Initial head
                   Adjusted head
               7. Comments on problems noted above.




              Comments From Homeowner.



              Additional Observations.













                                                                                                            31








         WASTE WATER SYSTEMS, INC.






                "PERC-RITE"Tm


        WASTE WATER DISPOSAL SYSTEMS






        Design Guidelines and Manual


         (Residential Sized Systems)




               Copyright 1992


                  Rev. 9-92




                                     TABLE OF CONTENTS




           Part One . . . .                          . . . . . . . . . .     1 -  3
           Description of th@ *-'P@r*c-Rite"T"
           Waste Water Disposal System


           Part Two  . . . . . . . . . . . . . . . . . . . . . . . . .       4    5
           Site and Soil   Requirements and
           Consideration   for "Perc-Rite"Tm Systems

                 General Space Requirements
                 Soil Requirements
                 Topography
                 Drainage Requirements


           Part Three  . . . . . . . . . . . . . . ... . . . . . . . .       6   21
           Layout of the "Perc-Rite"T" System

                 Size of the Absorption Field
                 Location of the System
                 Size of Septic and Pump/Dosing Tanks
                 Depth of Lines
                 Landscaping and Drainage


           Part  Four  . . . . . . .                                        22   54

                                          n
           Drip  System Dosing and D@slg*

                 Flow Rate during Absorption Field Dosing
                 Distance between Emitters
                 Field Flushing Flow Rates
                 Total Flow Requirement of System
                 Pump Size Verification
                 Calculating Flow Losses and Requirements for
                      "Perc-Rite  , TM W-20 Systems
                 Summary of Calculations for Pump Size Verification
                 Determine Absorption Field Total Operating Flow
                 Determine System Head and Friction Loss
                 Calculate Total Pressure Loss Consideration
                 Checking Design Pump Size
                 Design Modifications to meet Performance Specifications
                 Pump Specifications and Modifications
                 Modification of Design Layout
                 Design of Unequally Sized Absorption Fields
                 Unequally Sized Absorption Fields Dosed as One Zone
                 Unequally Sized Absorption Fields Dosed Separately
                 Time Operated Dosing
                 How to Set Up Dosing with the "Perc-Rite"Tm System
                 Example of Dosing Separate Fields of Equal Size
                 Example of Equal Sized Fields Dosing Separate
                 Dosing Unequal Absorption Fields Separately
                 Dosing Volume and Pump Float Switch
                 Summary
                 ."Perc-Rite" Tm Designs on Sloping Ground





                                  TABLE OF CONTENTS
                                       (Cont.)





          Example Design Calculations  . . . . . . . . . . . . . . . 55  63
          For "Perc-Rite"T" Systems
          Using This Manual

               Example Design 1
               Begin Design
               Calculate Flow Loss and Pressure Requirement
               Check Pump Performance
               Pump Float Switch
               Example Design 2
               Begin Design
               Calculate Flow Loss and Pressure Requirement
               Check Pump Performance
               Time Dosing
               Field Dosing Flows
               Pump Float Switch
               Designs not Meeting Performance Capabilities of
                    the "Perc-Rite"Tm W-20 System


          Part Five  . . . . . ... . . . . . . . . . . . . . . . . . 64  68
          Other Specifications and Equipment
          Used in the Complete "Perc-Rite"Tm System

               Septic Tank and Dosing Tank
               Pipes and Fittings
               Air Vents
               Electrical Service
               Home Water Saving Devices
               Site Preparation Specifications
               Final Landscaping
               Design Worksheet for "Perc-Rite"Tm Specifications


          Part Six . . . . . . . . . . . . . .* * * * * * * * * ' *  69   70
          Modified "Perc-Rite"Tm Systems Using Fill

               Design of Fill or Mound Systems
               Installation











           PART ONE

           Description of the "Perc-Rite"'
           Waste Water Disposal System






                The "Perc-Rite  TM Waste Water Disposal System is an improved
           soil absorption system for waste water disposal. A soil absorption
           system must serve two purposes: 1) keep untreated effluent below
           the surface, and 2) treat the effluent before it reaches ground or
           sur.face water. The system works best when the distribution area is
           not saturated with water or effluent, allowing efficient aerobic
           bacteria to treat the wastes.


                There are several conditions which frequently hinder the
           operation of soil absorption systems.    Clogging of the soil can
           occur from localized overloading during use or from the mechanical
           sealing of the soil-trench interface during construction.       This
           clogging can cause effluent to break through to the surface,
           especially in fine-textured soils. Anaerobic conditions caused by
           continuous saturation due to overloading or a high water table
           retard treatment, increasing the potential for pollution. Shallow
           soils are not deep enough to purify the effluent.

                The "Perc-Rite 1, TM System has five basic design improvements
           over conventional or L.P.P. type systems to overcome the above
           problems. The improvements are as follows:

                     - Uniform distribution of effluent
                     - Accurate control of effluent emission rates
                     - Dosing and resting cycles
                     - Shallow installation of drip lines
                     - Filtering of effluent before dispersal

                Problems from local overloading are decreased when effluent is
           distributed over the entire absorption area. Dosing and resting
           cycles help maintain aerobic conditions in the soil, improving
           treatment.   Shallow placement increases the vertical separation
           from the system to any restrictive horizon or seasonally high water
           table.

                A "Perc-Rite,,TM System is a shallow, slow rate pressure dosed
           soil absorption system.    The basic components of which are as
           follows:



                                                                              1








                      -  Septictank, sand filter or aerobic treatment unit
                      -  Pumping chamber/dosing tank
                                   ,, TM
                      -  "Perc-Rite   pump and controls
                      -  "Perc-Rite Tm automatic back flushing filters
                      -  "Perc-Rite TM pressure compensating waste water  drip
                         line laterals
                      -  Supply and return manifold lines
                      -  Alarms
                      -  Suitable soil absorption area

                 The "Perc-Rite 11 TM Filtering and Sub-surface Distribution System
           is operated via a "state of the art" controller which is activated
           by a sensing device located in a dosing tank downstream from
           pretreatment.    When activated by the level of effluent in the
           dosing tank, the controller will start the disposal cycle and pump
           the effluent through a 115 micron disc filter.            The filter
           configuration is modular and can be -amplified according to
           individual system needs. The degree of filtration (m:Lcrons) may be
           increased or decreased according to needs.

                 The inlet manifold carries the unfiltered effluent to the
           filter. The effluent.passes through the filter main valve, then
           through the filter itself, while the filter back flushing valve
           remains closed.    The filtered effluent flows through the outlet
           manifold and is discharged below the soil surface through a
           patented chemical- resisting, pressure compensating "drip" poly-
           tubing.   The construction of the "RAM drip" tubing is unique in
           that the internal diaphragm and labyrinth provides for an exact
           amount of effluent to be discharged from each of its emitters which
           are normally spaced at two foot intervals along its entire length.
           The "RAM drip" tubing maintains a constant dripper flow over
           pressure ranges of 5 up to 60 psi.         Because the effluent is
           distributed at a relatively low rate, large quantities of effluent
           may be distributed over long periods of time without saturating the
           surrounding soil, thus eliminating the possibility of run-off or
           surface water ponding.       When the back flushing schedule is
           triggered, the filter valve closes, thus blocking the flow of
           unfiltered effluent to the filter.       Af ter a short delay, the
           flushing valve opens, thereby discharging the filtered impurities
           into the collector manifold. The closing and opening procedure of
           the filter and back flush valves causes a change of flow within the
           filter.   When the f ilter valve closes, the upstream pressure is
           blocked, while the downstream pressure reverses the f low of the
           filtered  ef f luent back through the outlet of the f ilter.       The
           inverted  flow carries accumulated particles from the filter rings
           through the open back flushing valve through the collector manifold
           to the influent side of the pretreatment tank.       The back flush
           procedure lasts approximately fifteen seconds, upon where the back
           f lushing valve closes, then the filter valve opens and the inverted
           flow is cut off.    Only after the first filter has completed its
           flushing cycle, will the second filter begin its cycle of back
           flushing in the same manner as the first filter. The dripper lines

                                                                                2









          are automatically flushed every 200 dosing cycles. This function
          is activated by the controller which opens the field flush valve,
          thus allowing the flushed effluent to be returned to the
          pretreatment tank.    The duration of this cycle is approximately
          three minutes. The flushing action creates a high velocity of the
          effluent which produces a cleaning action over the inside walls of
          the dripper tubing, P.V.C. manifolds and emitters.

                The Telemetry Equipment monitors the following functions:

                          High water alarm (audio)
                          Power out alarm (audio)
                          Pump start control
                          Timed back flush of filters
                          Automatic flushing of drip system
                          Flow variance
                          Remote monitor of alarm functions

                In the event of a power outage or a high water condition, an
          audio alarm will sound. Simultaneously, the service center can be
          notified via- telephone link up through a digital communications
          receiver.   Should a flow variance (plus or minus 20%) occur, a
          signal will be transmitted to the service center indicating this
          trouble. A minimum of 24 hours storage capacity is designed into
          the system should a power failure occur.

                Since the field distribution lines require very little soil
          disturbance and effluent discharge volume from each emitter hole is
          insignificant, installation of the system has very little site
          impact even in established lawns and gardens. There are no visible
          indications that the installation site is being used for disposal
          purposes.    This distribution system will permit waste water
          disposal in land areas that are used for such purposes as parks,
          athletic fields, groves and highway rights of way. This system is
          especially suited for landscaped or wooded areas around buildings,
          trailer parks, apartment complexes or residential subdivisions.

                For existing or new treatment facilities - residential,
          commercial, industrial or municipal - our filtering and sub-surface
          distribution system can be a viable alternative to land application
          techniques (spray) or direct stream discharge.




                                        PERC-RITE PUMP
                                        & FILTER

                               ITARY TEE
                                                               rDRIP FIELD

              t-TWO COMPARTMWT  t- DOSING TANK
                SEFnc TANK
                             SAN
                    @R                    ;@<                                 3

                             FIGURE I - aASiC COmPONUM OF PERC-Rrrr sysTEm











           PART TWO


           Site and Soil Requirements and
           Considerations for "Perc-Rite"'" Systems

           (General Guidelines)






                The suitability of a "Perc-Rite  11TM System for a given site is
           usually determined by soil and its limitations, site slope and
           landscape characteristics and the available space for absorption
           systems as well as the anticipated waste water flow. The criteria
           below is a set of guidelines to follow to practically determine
           site suitability.


           General Space Requirements

                The drip field network of lateral lines for most residential
           "Perc-Rite 1 TM Systems can occupy anywhere from 1,000,square feet up
           to 10,000 square feet of area depending on soil texture and
           permeability and design waste water load. In some cases, according
           to local regulations an area of equal size may need to be set aside
           for repair areas. The septic tank, aerobic treatment unit, dosing
           tank and distribution field are also subject to set back
           regulations to keep required distances from wells, property lines
           building foundations and bodies of water according to local
           regulations. Calculating space requirements will be discussed in
           Part Three of this manual.



           Soil Requirements

                A "Perc-Rite 11 TM System should -be situated on the best soil and
           site on the lot.      A minimum of 24 inches of usable soil is
           recommended between the bottom of the drip line tubing and any
           underlying restrictive horizons such as consolidated bedrock or
           hardpan, or the seasonably high water table.      In some cases, as
           ,determined by the soils engineer or soils scientist for the site,
           the minimum usable soil depth may be reduced to as little as 12
           inches.   The "Perc-Rite 1,Tm drip lines may be installed as shallow
           as 6 inches or less (depending on soil characteristics and freezing
           depths) making minimum soil depth requirements easier to obtain
           than when using conventional systems. The usable soil must be of


                                                                                4









           suitable or provisionally suitable texture,           structure and
           permeability as defined in the " Perc-Rite 11 TM loading rate guidelines
           or state regulations.     IIn some cases, where the depth to the
           seasonable high water table or the restrictive horizons is less
           than recommended, a modified "Perc-Rite    , TM System using imported
           fill may be installed. Great care must be used in building these
           fill systems. Their design and construction are covered in this
           manual.



           Topography

                 "Perc-Rite"' System designed on slopes usually do not require
           special design and installation procedures.       Head losses due to
           elevation changes should be considered to ensure standard pump
           sizing will deliver the required . flow and pressure.       Since the
           "Perc-Rite" TM pressure compensating dripper emission rates are
           consistent at varying pressure differences, no special design
           requirements to ensure proper soil loading rates are needed-.
           Normal spacing between dripper line laterals is 24 inches.          On
           severe slopes of 20% or more, the dripper line laterals may need to
           be spaced wider than normal due to gravitational effects on water
           movement. Topography considerations are further discussed in this
           design manual.


           Drainage Requirements
                 Depressi'ons, gullies, drains and erosional areas must be
           avoided to prevent hydraulic overloading by surface runoff.
           Neither the septic tank, pumping chamber nor distribution field
           should be located in such areas.         Surface water and perched
           groundwater must be intercepted or diverted away from all
           components of the "Perc-Rite  11TM System. Site modifications to the
           "Perc-Rite" TM system area may be required to ensure all surface or
           perched water will be intercepted.

















                                                                                 5











           PART THREE


           Layout of the "Perc-Rite"' System






                The next few parts of this manual are a step by step procedure
           for correctly designing a "Perc-Rite 11 TM System. There is no single
           "Perc-Rite" TM System layout or unit that fits all sites - each must
           be designed individually.


           Size of the AbsQrRtiori Area

                The total amount of absorption area required generally depends
           on two factors: 1) the daily waste water flow of the facility or
           home being serviced by"the system and 2) the absorption capacity of
           the soil.



           STEP 1:

                Calculate the estimated daily flow. For residential systems,
           usually the local health department will assign a flow in gallons
           for every bedroom in the house.

                Example: Assign flow of 150 gallons per day per bedroom for
           a three bedroom house.


                Flow = 150 GPD x 3 Bedrooms = 450 Gallons Estimated Daily Flow


           STEP 2:


                Determine the loading rate.

                A field evaluation of the soils at the site must be completed
           by a qualified person (i.e. soil scientist). The data gathered at
           the site should include all the information necessary to completely
           fill out the Site Evaluation Sheet as shown (see Soil Form on Page
           15 and 16). Upon review of the completed Soil Information Sheet
           and a site investigation, a maximum hydraulic loading rate is
           established using Table 1 (the USDA Soil Classes and Maximum
           Loading Rate Table on Page 17).        Table 1 shows the Maximum
           Hydraulic Loading Rate that should be used for each soil group.
           See the notations at the bottom of Table 1. Chart 1 (See Page 18)


                                                                              6








            is an example of how soil textures are determined on the bases of
            clay percentage. Maximum loading rates will be stated in gallons
            per day per square feet. Note: In fill systems, soil fill must be
            closely monitored and evaluated as discussed later    in this manual

                 Example: Determine a loading rate. Soil investigation shows
            Class III - Sandy Clay Loam (SCL) use a maximum .15 gallons per
            square feet per day loading rate. Let's assume in this particular
            case that land room is not restrictive so we can use an even more
            conservative loading rate as a safety factor - (SCL) carries a
            maximum .15 loading rate. So we will use a .1 gallons per square
            feet per day loading rate.


            STEP 3:

                 Compute total area necessary    for the absorption field.     Use
            the following equation:

                                             Daily Flow
                      Area necessary      -----------------
                                          Daily Loading Rate

                 Example: Using the flow as calculated in Step 1 and Step 2.

                                          450 GPD
                 Area necessary     -----------------       4,500 Square Feet
                                     .1 Gal/Day/Sq.Ft.


            STEP 4:

                 Determine the total length of dripper line required in the
            absorption area.    Spacing between dripper lines is normally 24
            inches.   The equation to determine total length of dripper line
            required would then.be:

                 Total Absorption Area in Sq. Ft.
                 --------------------------------        Length of Dripper Line
                       Dripper Line Spacing

                 Example:

                      4,500 Square Feet
                 ----------------------------       2,250 Linear Feet of Dripper
                        2 Foot Spacing              Line Needed


            STEP 5:


                 Determine layout and shape of the dripper line absorption
            field.


                                                                                  7








                When selecting the best layout and shape of the dripper line
           absorption field you must always place the dripper lines along the
           contours of the ground area, keeping the dripper line lateral runs
           as close to the same grade as possible.      However, a completely
           level lateral run is not required. Also, always try to keep each
           individual dripper line length no greater than 400 feet from its
           connection to the supply manifold to its connection to the return
           flush manifold because of excessive friction loss. Some examples
           of dripper line layouts are shown in Figure 2 (see Page 9) and
           Figure 3 (see Page 10). Always configure the system supply line to
           feed at the lower end of the dripper field lines and return from
           the highest elevations.

                When running a continuous dripper line that may turn and make
           a loop or series of loops back to the return flush line before
           making a connection, make a transition to solid tubing that will
           resist kinking and does not emit effluent-in the turn, as shown in
           the example in Figure 4 (see Page 11) and Figure 5 (see Page 12).



           IMPORTANT:


                in many cases where dripper line lengths exceed a total of
           1, 000 feet or more it will become necessary to split the absorption
           field into at least two zones. This is required because a large
           system with over 1,000 feet of dripper line or more has an
           operating flow rate that will probably exceed the capabilities of
           the standard "Perc-Rite 91 TM unit. By using two or more zones, this
           problem is easily overcome and is described more in depth later in
           this manual. (See Drip System Dosing and Design.)


                REMEMBER: Always configure the layout of the system so that
           the effluent supply line to the dripper lines feeds the system from
           the lower elevation and layout the return field flush line from the
           highest elevation of the dripper field.


           Other Considerations in the Layout of "Perc-Rite   , TM Systems


           Location of the System

                The "Perc-Rite  I TM System should be located in the best
           available soil on the  lot.   All setback requirements from wells,
           lot lines and waterways must be observed (see Figure 7 on Page 14. )

                A repair area may'need to be designated if required by the
           local health department.     The exact location of the tanks and
           drainage or landscape improvements must be noted.



                                                                               8








                                                  FIGURE 2







                                           .HOUSE






                                                                        Ar-PERC-RITE'


                                        BACK FLUSH LINE ....... --


                                                           TREATMENT
                                                            TANK


                                 FLOAT SWITCH POWER LINES (2)


                                                              TAW


                                                              SUCTION LINE





                                                                                              ALR VENT 0
                                                                                              HN*93T POiNT


               4e    -SUPPLY LINE




                                                      FIELD FLUSH LINE














                     _PVC MANIFOLD
    PVC TEE            - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                       -----------------------------

                       ---------------


                                                               - - - - - - - - - - -      TEE
    PVC ME ----> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -n
                                              - - - - - - - - - - --m- - - - - - -         PVC MANIFOLD
                                                       ------------


                                                              - - - - - - - - - - -<____pVC TEE
    Pvc CIO    L- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -




                                                              - - - - - - - - - - -e-PVC
                                                                   . 9--nn"














                          RAN PRESSURE COMPENSATING DRY"'ER LINE
                         1200 LF. - 2' SPACING - 400' LATERAL RUNS





                                                COMMON RETURN AND SUPPLY







                                                           HOUSE







                                                                                              A@--PERC-R


                                                       BACK FLUSH LINE-


                                                                             TREATMENT
                                                                               TANK


                                              FLOAT SWITCH POWER LINES (2)


                                                                                 TANK


                                                                                 SUCTION LINE


                                  SUPPLY LINE

                                                                      FIELD FLUSH LINE

                                  PVC MANFMD
            PVC TEE-to - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                                                                                                                    AIR VENT 0
                                                                                                                    HIGHEST POINT
            PVC TEE    t, - - - - - - - - - -                       - - - - - - - - - - - - - -           <----WC TEE

                                                                                                          4E        PVC MANIFOLD


                                     RAM PRESSURE COMPENSATING DRIPPER LINE       - - - - - - - - - - -   <----- PVC TEE
                                     600 L.F. - 2' SPACING    300* LATERAL RUNS


                                  PVC MANIFOLD                         FIELD FLUSH LINE



                                  PVC MANIFOLD
            PVC TEE
                        :@   ----------------------------------
                            - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --           e-Pw Ta
            PVC TEE     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --
                                                                            -- I -- -- - - - - - - - -               AIR VENT 0
                                                                                                      :3      N      HIGHEST POINI
                                                                         - - - - - - - - - - - -
                                                                      - - - - - - - - - - - - - - - -     <-PVC TEE
            Pvc ci C)  -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --
                                                                                                           4E       PVC MANIFOLD
                                                     ----------------------


                                      RAM PRESSURE COMPENSATING DRIPPER LINE
                                     1200 L.F. - 2* SPACING - 4400' LATERAL RUNS
                                                                                                                    10







                                             FIGURE 4





                                                                           Eftc-RITE DRIP TUB",G




                  ',@\@PVC FEMALE ADAFrER      ll\QUICK LOCK FITTING

                               OETAIL    QUICK LOCK FITTING





















                                                           PERC-RrrE DRIP TUMNG








                                                  QUICK LOCK FrMNC

                                                  PVC FEMALE ADAPTER




                              /r' FLEX PVC















                           DEML - 7YPICAL ORIPUNE CONNECTION IN TURN OR LOOP







                                                     FIGURE 5
































                              DRIPPER LINE




                    FINISHED GRADE







                                                                                              hy



        PVC PIPE-)

                 PVC TEEE




                              EARTHEN DAM IN TRENCH
                              TO PREVENT FLOW ALONG
                              FLEXIPVC LOOP                      -71




                               SECTION - DRIFPER LINE TO FOLLOW CONTOURS
                                dc PVC MANIFOLD PERPENDICULAR TO GRADE









                                                                                                        12









                                                      FIGURE 6












                  1 -1 Ir PVC PIPE




                  1-1/2 x 1-1/2 x 1/2
                  REDUCING TEE



                                                                                     FLEX PVC


                  1-1/2 PVC PIPE



                                                                                           DRIPPER LINE
                  2xl-1/2 REDUCING BUSHNG


                  20xl/Z REMXVC TEE
                                                        PVC FELVA.E. ADAPTER




                                                                               QUICK LOCK THREADED
                                                                               FMMG





                                            FLEX Pvc







                                                    DRIPPER UNE














                                    TYPMAL DRIPPERLINE CONNWTION TO PVC

                                     (MAY VARY ACCIORDING TO MAN FA=REWS
                                       SPECSIMMYTONS)


                                                                                                     13









                        A. LOCATE SUMABLE, AREAS ON SITE




                                                       -T
                                                       ......                                     I O'T Lar SEr BACK


                                                                                                  AREA DETERMLNED MOST
          UNSUITABLE                                                                              SUMABLE BY SOIL
          SOIL                                                                                    EVALUAMON






                                                                                                  100' SET BACK FROW
                                                                                                  WELL











                                                                                                  WTI I










                         IL SPECIFY Lccxna* oF svsmi
                         7--                            --                  -----7
                                                .......................

                                                                                                   REPAIR AREA
                                                                                                   (IF REQUIRED)
                                                                                                   60' X 30*



                                                                                                   ABSORPTION FIELD
                                                                                                   60' X 80'


            PERC-RffE
            UNIT

                                                                                                   PUMPING TANK


                                                                                                   SEPTIC TANK





                                                                                                   5 BEDROOM HOUSE













                                                                                                             14
                                                       FIGURE 7








                                                                             SOIL FORM



                  OUNER:                                                TELEPHONE 1:                           DATE:

                  ADDRESS:                                              GURU/LDT/BLDCK:

                                                                        COUNTY:                                EST, FLOU RATE (CPU):

                  SOIL SCIENTIST:


                  NOTES:









                                                                   DEPTH 19 GROUND
                 HOLE         SOIL          SLOPE/   LANDSCAPE/    UAIER OR OTHER                CULLEY                                  FLOOD
                 tin,        SERIES                    ASPEEI     RESIRIVIVE LAYER                DATA                  EROSION          HAZARD



















                ul
                                                                              SIDE ONE



                                                                                                                                           0



                                                      MOIST COLOR                                                    PERME-      PERE         7     VAX Oyu
                   ROLE                                                           A)                 (9)            ABILITY      RATE       OF      LUAU INC
                   flu,               INCHES)     MATRIX       NOTILEG        TEXTURE           EUNGIGIENCY         INEH/RR    NIN/INER    G7DNE     RATE
                                      DEPI





































                  AggREVIA]IDIIS:      A)   G.E.G.    SOIL:   Sand   G;  Loomy Gand    LG; Sandy Lear,     GL; Lear,   L; Gandy Clay LGRA      GEL;
                                            Gilt Lair, - GIL; Clay Lear, - EL; Silty Elay Laim - GIEL'; Gandy Clay - GE; Silly Clay           GIE; Clay    E.

                                      (9)   S.E.S. - CONSISTENCY:    Loooo - ML; Very Friable - NVFR; Fpiablo - NFR; Fipri - KFI; Very Firm - WVFI;
                                            Extpimoly Firm - NEFI.

                                                                                    G IOE lug






          Table I shall be used in determining the acceptance rate f or drip
          systems.    The acceptance rate shall be based on the most
          hydraulically limiting, naturally occurring soil horizon within two
          feet of the dripper line bottom.





                                        TABLE 1



          S= GROUP          SOIL TEXTURAL-CLASZEa           MAXIMUM HYDRAULTr-
                           (U.S.D.A. CLASSIFICATION)             LOADING RATE


                                                                    rynrl f -t-2.


                        Sands                  Sand- S                     0.4
                        (With S or PS          Loamy-Sand - LS
                        structure)


                        Coarse Loams           Sandy Loam - SL             0.3
                       .(With S or PS          Loam - L
                        structure)


            III         Fine Loams             Sandy Clay Loam    SCL     0.15
                        (With S or  PS         Silt Loam - SIL
                        structure)             Clay Loam - CL
                                               Silty Clay Loam    SICL


             IV         Clays                  Sandy Clay - SC              0.1
                        (With S or   PS        Silty Clay - SIC
                        structure)             Clay - C



          Note: The acceptance rate shall be   less than the maximum hydraulic
          loading rate for the applicable soil group for food service
          facilities, meat markets, and other places of business where
          accumulation of grease can cause premature failure of a soil
          absorption system. However, acceptance rates up to the maximum for
          the applicable soil group may be permitted for facilities where
          data from comparable facilities indicates that the grease and oil
          content of the effluent will be less than 30 mg/1 and the chemical
          oxygen demand (C.O.D.) will be less than 250 mg/l.

          Remember: These are Maximum Rates. If textures seem inconsistant
          or there is adequate room, a lesser loading rate may be used.






                                                                             17










                                                          Chart 1







                                  cIIkRT1 GUIDE 70F USDA SOIL


                                                           100

            using Matw%ais Laos Tfum                                                              Ex- Le of Use:
            2.0 =tM. iM SiMP_ If AVPMX-
                                                                                                   A soil material
            20%,or ==m of the soil                     -90                                         with 35% ciny,
            =&"Sid is Urger th=                                                                    30% silt and
            ZO lum. the                                                                            35% sand is a
            awm inciucim a                       so                              1z                ciav loam.
            mxmdifwr. R--vie:
            gravefly sandy icamL

                                             7





                                   N)o

                                  so 1.                                           .3itty



                                                             Tjav icam               loam
                        30
                                san0y imay iuam


                   20
                                                             i0am
                                                                        409                               IN
                                     . ...............                   ----------- ilt loam
                                      sanav loam
                                                                 =Z_
              10


                           San


            VO-1


                                                          Dercem sanc
                                                        10





















































                                                                                                                 18












                                   EXAMPLE OF FORM FOR:


                              SITE EVALUATION SPECIFICATIONS





          PROJECT


          OWNER                                             PHONE


          LOCATION


          DATE


          COUNTY




          SOIL TYPE                              SOIL TEXTURE


          SOIL GROUP                             DEPTH FOR OPTIMUM USE


          SOIL LOADING RATE                      PROJECTED DAILY FLOW


          DISPOSAL AREA SIZE                G.P.D.          L/R           SQ. FT.

          TOTAL DRIPPER LINE (2' LATERAL SPACE)            SQ FT t 2           L/FT

          SITE SLOPE                             When slopes of  20% or greater
                                                 are encountered use three (3)
                                                 ft. minimum lateral spacing.



               ABSORPTION FIELD REQUIRED PER     100 GALLONS OF WASTE WATER
                LOADING RATE               SQUARE FEET                 LINEAR FEET
                    0.4                          250                         125
                    0.3                          333                         167
                    0.15                         666                         333
                    0.1                          1000                        500
                    0.05                         2000                       1000


          Formula For Computing Linear Footage For Other Loading Rates:

          AREA REQUIRED:

                 allons Flow/Day         Area Required
                Loading Rate             Square Feet

          LINEAR FEET DRIPPER LINE REQUIRED:


                 Area                    Linear Feet
                Lateral Spacing                                                 19









           Size of Septic-and PUM/Dosing Tanks

                Septic tank volume is determined according to state and local
           regulations, and is the same as a conventional system. The pumping
           tank should provide one day for emergency storage; therefore, twice
           the volume of the daily flow would definitely be sufficient.

                Example: For a 450 GPD waste flow.

                Volume of Pumping Tank = 450 Gallons x 2 = 900 Gallons

                Aerobic treatment units (ATU), if used as the means of waste
           water treatment, should be sized by local health authorities and
           ATU manufacturer.



           Depth of Lines

                Lines may be placed anywhere in the soil profile that has been
           determined by the soils engineer to be the most acceptable depth.
           Normally, however, line depths are usually from 8 inches deep to 24
           inches deep.   This depth is often determined by the restrictive
           horizon in the soil in order to meet the separation requirement.
           The shallowest installation possible should be used as shown in
           Figure 8 (see Page 21).


           Landscaping and-Drainage

                All landscaping, filling and site drainage completed before
           and after the "Perc-Rite   , TM installation must be recorded and
           evaluated to ensure the integrity of the soil absorption system.
           Use of imported fill must be done in accordance with procedures
           described later in this manual (see Modified "Perc-Rite  , TM  Systems
           using fill in Part 6.)



















                                                                             20







                                                     FIGURE 8

























               7MLS DEPTM VARIES


                                                                                                             YPICAL
                                                                    FlNIISHED GRADE


                                                                                                      V-

















                                          7 4f O.C.

                                                                              MOTE. UNES  MAY  BE INSTALLED
                                                                              ErY STHER PLOWING OR -RENCHING
                                                                              METMOD.


                                   IRRIGATION ORIP LINE iNSTALLATION 3E7;AIL
                                                                                                      v
                                                                                            @, @E Ll@


                                                                                                              21











           PART FOUR


           Drip System Dosing and Design






                The purpose of the "Perc-Rite   TI pressure compensating drip
           system dosing is to provide slow rate uniform distribution of the
           septic tank or ATU effluent over the entire soil absorption system.
           This is easily achieved using the type of dripper line incorporated
           in the "Perc-Rite 11 T11 System since -changes in pressure inside the
           tubing has little effect on the dripper emission rates. This part
           of the design manual will instruct you on how to ensure your "Perc-
           Rite 11 TM System components have been sized correctly.


           Flow Rate during Absorption Field Dosing

                The flow rate during absorption field dosing depends on the
           amount of dripper line required for any particular installation.
           The flow rates are easily calculated as follows:

                The "Perc-Rite  IT" RAM dripper line discharge rate is .61
           gallons per emitter. This discharge rate is constant from 5 to 60
           psi. (See Flow Chart - Graph 1 on Page 23.)


           Distance between Emitters

                In almost all cases, the distance between dripper line
           emitters will be a standard 24 inches. Therefore, the equation to
           calculate the absorption field dosing rate is as follows:

           Note: GPH = Gallons per Hour
                  GPM = Gallons per Minute

                Dripper Line Length in Absorption Field
                ---------------------------------------   = Number of Emitters
                          2 Foot Emitter Spacing

                Number of Emitters x .61 GPH = Absorption Field Dosing Rate
                                                 in GPH


                    GPH
                ----------      Absorption Field Dosing Rate in GPM
                60 minutes



                                                                             22








                Example: You have 2,000 feet of dripper line required in an
           absorption field.

                2,000 feet
                ----------    1,000 emitters in the absorption field
                     2

                1,000 x .61 GPH = 610 GPH

                  610 GPH
                ----------     10.16 GPM
                60 minutes
                Therefore you have a 10 gallons per minute flow in the
           absorption field during dosing.


                                         Graph 1.

           "Perc-Rite" Tm RAM Dripper Line Discharge Rates vs. Pressure







                                                                          <- Standard
                                                                             .61 GPH "Pei
                                                                            Rite" Dische
                                                                             Rate






                                                                 PROUM (PNI

                                     20                                   70





           Field-Flushing Flow RateS
                Since automatic flushing      of the dripper lines in the
           absorption field is an integral function of the "Perc-Rite"T" total
           system, it should be considered as part -of the overall flow rate
           generated by the system. This is important in determining if the
           standard "Perc-Rite 1, TM pump will be operating within its ef f iciency
           rating.
                It has been established that proper scouring and flushing of
           any pipe system will require at least 1.6 gallons per minute flow
           at the outflow end (distal end) of any pipe. Therefore, we should

                                                                               23









           require a f low of at least 1. 6 gallons per minute out of each
           dripper line connection that has been made to the return f lush
           manifold pipe. Therefore, multiply each return manifold connection
           by 1.6 GPM to get the field flushing flow requirement. This flow
           rate will be generated in addition to the absorption field dosing
           flow rate.

                Example: Assume you have 2,000 feet    of dripper line required
           in the absorption field. The field configuration and layout has
           allowed for 400 feet (maximum) lateral dripper line runs or loops
           before connection to the field flush manifold line.         Therefore,
           there will be five connections to the field flush line.

                Equation to determine the field flush flow requirement:

                5 connections x 1.6 GPM = 8 GPM


                So 8 GPM is required.

                Note:    Regardless of field layout or configuration, use at
           least 1.6 GPM multiplied by the number of return flush line
           connections.


                Example:

                1,800 linear feet of dripper line
                ---------------------------------    = 9 manifold connections to
                      200 feet lateral runs             flush line


                9 x 1.6 GPM = 14.4 GPM Flushing Flow


           Total Flow Requirement of System

                The total flow used in calculating the operating flow
           requirement of the "Perc-Rite    11 Tm absorption field would be the
           combination of both the field dosing flow and the field flushing
           flow.


                Example:

                2,000 L.F. Drip
                ---------------      1,000 Emitters
                       2

                1,000 Emitters x .61 GPH = 610 GPH

                 610 GPH
                ----------     10.1 GPM
                60 Minutes


                Therefore, you use 10 GPM.

                                                                               24









                 2,000 L.F. Drip
                 ---------------      5 Connections
                  400 Foot Runs


                 5 connections x 1.6 GPM     8 GPM

                 Total Flow Requirement     10 GPM + 8 GPM = 18 GPM

                 Therefore, 18 GPM is the Total Flow Requirement in this
           example.



           Pumr) Size Verification

                 To determine if the "Perc-Rite  1, TM System pump is the correct
           size, flow friction and head losses must be considered. Once the
           f low friction and head losses have been calculated and an operating
           pressure requirement has been established, this can be compared to
           the pump performance chart for the standard "Perc-Rite       1, TM  unit.
           This will determine if the system is designed within the operating
           capabilities of that standard system. If the system as designed
           exceeds the performance characteristics of the standard "Perc-
           Rite 1, TM unit, you may then modify the system design to work within
           the "Perc-Rite  1 TI operating capabilities.   Such as splitting the
           absorption field into two or more separate zones that operate
           independently, change pipe sizes, dripper line lateral lengths or
           any combination of these iti@ï¿½ms. Changing the pump size to larger
           than standard is also an option.       All of these options will be
           discussed in this section.

           Calculatincr Flow  Losses and R           its for "Perc-Rite"7" W-20
           Systems

           Friction and Head  Losses to Consider


                 A.   Suction Line Loss
                 B.   Suction Lift
                 C.   Pump Discharge Supply Line to Absorption Field-Force Main
                 D.   Return Flush Line Loss
                 E.   "Perc-Rite"  TI Pump and Filter Unit Loss
                 F.   Pipe Fittings
                 G.   Elevation Changes
                 H.   Dripper Line Laterals



           Calculation Methods


           A.    SUCTION LINE LOSS


                 Using Chart 1A, calculate the friction loss in your suction
           line from dosing tank to pump unit. 1 1/4" PVC schedule 40 is a

                                                                                25









           standard for the "Perc-Rite 11 TM suction line.

                How to -use t he chart.    After calculating the total flow
           requirement of your absorption field as discussed previously, find
           that flow in GPM in the first column of Chart 1A (see Page 34).
           Follow the line that corresponds to the flow requirement to the
           column under the pipe size at the top of Chart 1A (see Page 34)
           corresponding to your suction line size (remember 1 1/4" is a
           standard).   However, it is possible, due to system size, that a
           larger pipe size will make the system design more efficient. Find
           the loss number in that column for your design flow. This loss is
           in feet of head. Remember this head loss will be per 100 feet of
           pipe. In order to convert this head loss into psi pressure loss,
           divide this number by 2.31.     The 2.31 value is the conversion
           factor for finding pressure loss (in psi) out of the head loss in
           your pipe. Therefore, the equation for finding your pressure loss
           in the suction line is as follows:


                Head Loss in Suction Line from Chart 1A
                ----------------------------------------       PSI Loss
                                    2.31


                Note: Always use the next higher number in the chart if your
           calculated flow does   not exactly match the chart flow in GPM.
           (Example: Suppose the  design flow is 14 GPM. 14 GPM is not on the
           chart, so use 15 GPM, which is on the chart, as the flow.)

                Example:  System  absorption field total flow is 18 GPM (as
           calculated.in the previous example of finding operating flow.)
                Chart 1A shows 18 GPM in 1 1/4" pipe to lose 4.28 in head loss
           per 100 feet.

                Assume a 40 foot suction line length then loss is:

                      4.28 x .4 = 1.71
                                                       1.71
                Convert the head loss to psi:        ------  = .74 psi
                                                      2.31


                To be safe you may round to 1 psi; therefore, suction line
           loss is 1 psi.



           B.   SUCTION LIFT


                Check suction lift by elevation change from suction line
           intake to the pump location.     This number should be used when
           checking the pump performance in Chart 4A (see Page 37).        Pump
           performance charts show pumping depth in five foot increments.
           Round the actual elevation difference = to the nearest multiple of
           five when checking pump performance.


                                                                             26








                 Example: Intake of the suction line is 8 vertical feet lower
           than  the elevation of the "Perc-Rite,,TM pump unit location. Round
           the 8 feet = to the nearest multiple of five or 10 feet.

                 When checking pump performance, Chart 4A (see Page 34) as
           discussed later, use 10 feet as suction lift.



           C.    PUMP SUPPLY LINE TO ABSORPTION FIELD - FORCE MAIN


                 This calculation will be the same as described for suction
           line  loss. You will again use Chart 1A. The length of the supply
           line  from the "Perc-Rite,,TM pump unit to the farthest point in the
           absorption field area should be used in calculating this flow loss.
           You will again use the total flow requirement of the absorption
           f ield in GPM which is the first column in Chart 1A.          Find the
           column which corresponds to the supply line size intended. Use the
           loss column for that size pipe at the absorption field total flow
           rate. The conversion to pressure loss in psi will be the same as
           in the suction loss.


                 Head Los's
                 ---------      PSI Loss
                    2.31

                 Example:   Again using 18 GPM total flow, assume 1 1/4" supply
           pipe, Chart 1A   shows 18 GPM in 100 feet of 1 1/4" pipe is 4.28 head
           loss.   The supply line is 150 feet to the farthest point in the
           system. The loss is 4.28 x 1.5 = 6.42. Then convert to psi.

                 6.42 head loss
                 --------------      2.78 PSI Loss
                        2.31


                 The supply line to field loss is 2.78 psi.



           D.    RETURN FLUSH LINE LOSS -


                 The return flush line loss is figured in the same manner as
           the absorption    field supply line loss as discussed in Part C.
           Always remember  to use a return flush pipe size equal to the supply
           line size,    Use as your length of line for this calculation the
           total length of pipe from the "Perc-Rite    , TM pump/filter unit to the
           farthest point at which a dripper line lateral connects to          the
           return flush line.


                 Example: The flush line at the farthest point away from       the
           "Perc-Rite" TM pump/filter unit is 180 feet. The supply line to     the
           absorption field is 1 1/4", so the return flush pipe will be        the
           same size or 1 1/4".


                                                                                 27









                 Note: As discussed earlier, proper flushing velocities are
            calculated at 1. 6 gallons per minute per dripper lateral flush line
            connection.    Therefore, to calculate the flow used to. determine
            loss in return flush lines multiply 1.6 x the number of flush line
            connections.

                 The earlier example of total flow of 18 GPM was for a 2,000
            linear f eet absorption f ield with 400 feet lateral dripper line
            runs. Therefore, we will use five connections to the return flush
            line in this example.

                 Example: 5 connections x 1.6 GPM         8 GPM

                 Use 8 GPM as flushing flow through the return line.

                 Now use Chart 1A again to calculate losses through the flush
            line. Chart 1A shows 8 GPM through 1 1/4" pipe is .95 head loss.
            Suction line is 180 feet long. Therefore:

                                             1.71
                 1.8 x .95 = 1.71            ---- .74 psi (Round up to 1)
                                             2.31


                 Loss in return flush line is 1 psi.


            E.   "PERC-RITE it TM PUMP/FILTER UNIT LOSSES -

                 All the figures for pressure loss in the valves, flow meter,
            filters,   fittings,    etc.    of  the   "Perc-Rite" TM   preassembled
            pump/filter unit have been calculated and are found in Chart 2A
            ("Perc-Rite 11Tm Filter Unit Losses, see  Page 35). In order to find
            the flow loss through the "Perc-Rite"Tm Pump/Filter Unit, you will
            use the total flow rate calculated for the absorption field and
            find that flow rate in the first column of Chart 2A. The second
            column will give you the flow loss in psi through the unit..

                 Example:    Again use 18 GPM, as calculated previously.         The
            chart shows at 18 GPM pressure loss will be 10.35 psi. Therefore,
            the "Perc-Rite 1, TM Pump/Filter Unit Loss would be 10.35 psi in this
            example.



            F.   PIPE FITTINGS


                 During all calculations in determining pressure/head losses
            and requirements, you generally have been rounding up to the
            nearest whole number or as in the case of the suction lift, you
            always round up to the nearest multiple of five (as discussed in
            'Part B).    Therefore, the insignificant pressure loss through
            fittings in the "Perc-Rite    , TM W-20 residential system will not
            require any calculations and will not effect operation of the

                                                                                  28








           system as discussed in this section.         Use as few fittings as
           possible.



           G.    ELEVATION CHANGES

                 Changes in elevation will contribute to the total losses that
           need  to be considered. The area of the "Perc-Rite      , TM System which
           must  be considered for losses due to elevation changes is,:

                 The elevation dif f erence from the " Perc-RiteTm Pump Unit to the
           highest point in the absorption field.

                 Remember: As discussed earlier, you will always design the
           supply line to feed the drip absorption field from the lowest
           elevation of the absorption field and the return flush line feeds
           from the highest elevation in the.absorption field.

                 Converting elevation changes to pressure losses in psi. It is
           known that for every 2.31 feet in elevation rise the pressure
           required to overcome that elevation change is 1 psi; therefore, the
           equation to convert elevation change to pressure loss is:


                 Number of Feet in Elevation Rise
                 --------------------------------        PSI Loss
                               2.31



                 To find pressure loss in elevation changes, first determine
           the change in elevation rjjgae, if any, from pump/filter unit
           location to the highest point in the absorption field which most
           likely will be at the highest flush line connection.

                 Example #1: The pressure loss computation is as follows:

                 The elevation rise is 15 vertical feet from the "Perc-Rite"TM
           Unit  to the highest point in the absorption field.

                 15 feet Elevation Rise
                 ----------------------        6.49 (Round to 6.5 PSI)
                           2.31


                 The pressure loss in the elevation rise is 6.5 psi.


                 Example #2: The pressure loss computation is as follows:

                 The elevation rise is 0 vertical feet, or the field is
           approximately the same elevation as the "Perc-Rite"' pump unit.



                                                                                  29









                0 Elevation Rise
                ----------------      0 PSI Loss
                        2.31


                The pressure loss in the elevation rise is 0 psi.




          H.    DRIPPER LINE LATERALS -


                Pressure/ friction losses for the dripper line laterals or
          loops must be considered in the overall pressure requirements of
          the pump system.    This pressure is usually the most significant
          amount of pressure losses to consider.

                The calculation of the pressure requirement has been made
          simple by the use of Chart 3A ("Perc-Rite    11Tm Drip Line Pressure
          Requirements on Page 36).         The pressure requirements for
          maintaining the minimum required 5 psi operating pressure
          throughout the dripper line lateral has already been calculated and
          put on the chart for varied lengths of dripper line this chart has
          also taken into consideration the pressure required to maintain the
          1.6 GPM minimum flushing velocities in the dripper line lateral and
          friction loss.


                Simply determine the length of the longest dripper line
          lateral or loop in your system design and refer to Chart 3A (see
          Page 36). Find the corresponding inlet pressure requirement for
          the longest lateral length in your system.            This pressure
          requirement will then be the minimum required pressure to maintain
          correct dripper line operation and flushing throughout the entire
          absorption field since the longest lateral or loop was used in
          determining that pressure.


                Example: An absorption field requiring 2,000 feet of dripper
          line and having five lateral lines or loops. The longest lateral
          is 400 feet.      Chart 3A shows an inlet pressure requirement
          corresponding to 400 feet lateral length is 25.4 psi.

                The pressure requirement consideration for dripper line
          laterals is 25.4 psi in this example.


          Summary of Calculations for Pump Size Verification Procedure

                The first step in any design verification will have been the
          determination of the absorption field size, based on flow and soil
          loading rates. Then pump sizing verification will be as follows:




                                                                             30,










           Determine AbsorRtion Field Total ORerating Flow

                 2,000 Linear Feet
                 -----------------       1,000 Emitters
                  2 Foot Spacing


                 1,000 Emitters x .61 GPH Rate = 610 GPH



                   610 GPH
                 ----------      10.1 GPM
                 60 Minutes



                 Round off to 10 Gallons per Minute


                 5 Lateral Lines 400' Long x 1.6 GPM Flushing Velocity      8 GPM


                 10 GPM Operating  + 8 GPM Flushing = 18 GPM


                 18 GPM Total Operating Flow


                 Note:  Flushing flow will be   an important separate flow rate
           as discussed later in system modifications.


           Determine System Head and Friction Loss


                 A.  Suction Lin6 -     Use Chart 1A and 2.31 as a conversion
           factor.


                                                  40 Feet
                 1 1/4" Pipe at 18 GPM = 4.28 x   --------  = 1.71
                                                  100 Feet



                 1.71
                 ----  = .74 psi     (Round off to 1 psi)
                 2.31



                 B. Suction Lift - Determine vertical lift from the        suction
           intake to pump location - compare in pump Chart 5A when verifying
           the pump size.



                                                                                31








                C. Force Main     Again, use Chart 1A.

                                                  150
                1 1/4" Pipe at 18 GPM     4.28 x --- 6.42
                                                  100


                6.42
                ---- = 2.78 psi
                2.31



                D. Return Flush - Again use Chart 1A.

                5 Connections to flush line x 1.6 GPM      8 GPM



                                         .95 (Use 1)
                1 1/4" Pipe at 8 GPM =    -----------   .43 psi (Use .5 psi)
                                            2.31


                E.   "Perc-Rite"Tm Pump/Filter Unit   Use Chart 2A.

                18 GPM shows 10.35 psi.


                F. Pipe Fittings - No calculations required for "Perc-Rite"Tm
           Residential Units.



                G. Elevation Changes

                Number of Feet in Elevation Rise
                --------------------------------   = PSI Loss
                               2.31



                Elevation rise = 2 feet



                                           2 Feet
                Total Elevation Loss       ---------- = .86 (Round to 1 PSI)
                                            2.31



                H. Dripper Line Laterals - Use Chart 3A.

                The longest dripper line lateral is 400 feet. Chart 3A shows
           25.4 psi requirement corresponding to 400 feet lateral length.
           (Use 25.4 psi)



                                                                               32









           Calcul e Total Pressure Loss considerations

                A.   Suction Line -                                  1.00 psi
                B.   Suction Lift - To be used in pump Chart 4A
                C.   Supply Line -                                   2.78 psi
                D.   Return Flush -                                  1.00 psi
                E.   Pump Filter Unit                                10.35 psi
                F.   Pipe Fittings -                                 0.00 psi
                G.   Elevation Changes                               1.00 psi
                H.   Dripper Line Req.                               25.40 psi

                Total Pressure Required   (Add A-H together)
                                                                    41.53 psi









































                                                                             33




                                            Riction loss in plastic pipe = Schedule 40

                                                                                                                                               CHART 1A.
                                   Veiocity measured in ft./sec., Loss in                                       feet of water head             per 100 ft. of Pipe-
                                            GALL                           3/4.                                 11/4, 1                        11/2,  2-                  2 1/2'               3'                  3
                                            PER
                                            311N.     Vol Lou        Ved       Lou             Vel              Less Vol       LAM Vol         Less Vol         Lou       Vel             LOM Vol Lou Vol L" Vol LAM
                                            I         Z.10 3.47      1.20      0.69
                                            4         4 23 12.7      2.41      Y29             1.49             1.01 86        27 63           .12
                                            6         6 )4 26.6      3@61      6.91            1.23             2.14 1.29      57 94           .26  .57         .09
                                            8         8.45 46.1      442       11.8            IM               3.68 1.72      .91 1.26        -45              .16       .52             05
                                            to        JC)669.1       602       17.9            3.72             5.SO 2.14      1.44- I-S7      .67  .96         .24       6s              09   43        .01       1
                                            12                       7.22      14.9            4.46             7.71 2.57      2.02 1.89       9-4 1.15         .37       .78             11   52        Os
                                            I 1                      9.02      37.6            5.60             11.6 3.21      3.05 2.16       1.41 1.50        '51       99              17   65        07        .49        .03
                                            1                      10.8        50.9            6.69             16.S 3.86      4.28 2.83       1.99 i.n         .7o       1.18            24   78        .10       'A         .04
                                                                           0
                                            .0        S, PIPE      12.         61.9            7.44             19.7 4.29      S.21 3.15       2.44 1.01        46        111             .29  87        12        61         01         -$1       .01
                                            25                                                 910              SOA S.36       7.90 3.80       3.43 2.50        1.28      1.61            41 1.09        is        al         08         .64       .04
                                            30        49        02                             11.15            41.9 6.43      10.9 4.72       S.17 2.89        1.80      1.96            161 1.30       .2s       97         .11        T7        .06
                                            35        57        .03                            13.02            55.9 7 51      14.7 S.Sl       6.91. 3.35       2.40      2.35            al 1.52        3)        .1.14      .15        '89       .06
                                            40        61        .04        6'  PIPE            14.68            71.4 9.58      19.8 6.30       9.83 ).92        3.10      2.68            1.03 1.74      43        1.30       19   1.02            .10
                                            45        113       04                             16-70            96S            23.5 7.08       10.9 4.30        3.55      3.02            1.12 1.95      S4        1.46       24   1.15            .13
                                            50        32        05         57       .02                         0.72           28.2 7.97       13.3 4.78        4.65      3-3S            1.56 :-17      .6S       1 @62      29   1.28            .16
                                            55        90        06         62       02                          1111.78        33.8 6.66       16.0 5.26        S-55      369             1-88 2.19      74        1 70       )4   1.41            19
                                            60        98        07         .68      0)                          12.87          40.0 944        IS-6 5.74        6.53      402             2.19 2.60      90        1 95       40   1.53            22
                                            5         106       09         @74      04                          iIII 92        46.7 10.21      21.6 6.21        7.56      4'36            2.53 2.82 1.02           2.00       47,  1.66            .25
                                            -         4                                                                                                                                   304       1.21           2.27       54   1.79            .30
                                            M         1.1       10         79       .04                         15 01          $3.1 11.02      24.9 6.69        9.64      4,69            2.91
                                                      1         1                                                                                                                                   1.41           2.12
                                            Is        12        1          as       051                         1606           60.6 11.80      26.2 7.17        9.92      5.01            3 35 3 25                           60   1.91            34
                                            -;0       111       11         91       as                          1716           69.2 12.69      32.0 7.6S        11.1      5.36            3@71 3A9  I.S4           260        69   2.04            .38
                                            95        L' 19     15         96       06                          118 21         T7.0 MIS        3S.3 9.13        12.5      S-70            3.8113 69 1.66           2.62       76   2.17            42
                                            90        1 47      16   1 02           07                          119 30         846 14 71       19-S 9.61        118       6.03            461. 3 91 1 92           2.92       as   2.30            .47
                                            95        1 55      191  1.08           07                          1              14.95           43.7 9.08        IS.)                      4 12      2.04           2 93       96   2.42            53
                                            100       1.6)      19   1 13           09                                         5.74            479 956          16.8      6.70            5,64 4 34 2.33           125        101  2.55            -S7
                                            110       1.79      1.1  115            10                                         117.31          S7') I&S         M.2       7.17            6.91 4 77 1.82           3 57       1.25 2.81            @69
                                            120       1'96      .27  1.%            11         S'               PIPE           18*89           67.2 11.5        21.5      9.04            789 5.21  3.29           3-99       1.45 )ob             .80
                                            130       2,12      31   1 47           13                                         20.46           78.0 12.4        27.3      6.71            9.79 564  341            422        1.68 3.31            .9)
                                            140       2.29      .36  1.59           Is         90               04             12.04           99.3 13.4        31.5      9.38            10.5 6.06 4.32           4.54       1 93 3.57            1.07
                                            150       2,45      41   1.70           .17        %                04             23.6            14.3             35.7      10.00           12.0 6,51 491            497        2.19 3.92            1.21
                                            160       1.61      46   1. BD          191        1.02             051                            15.3             40.4      10.7            13.6 6.964 S.54          5.19       2.47 406             I.S7
                                            17U       IM        51   1.92           21         log              OS                             16.3             45.1      11.4            16.0 7 56 6.25           512        2.75 43S             I.J)
                                            Iso       2.94      57   1.04           .24        1.15             06                             17.2             50.5      12.1            16.8 781  6.58           SAS        3.07 4.60            1.70
                                            190       3.10      .63  2.16           .26        1.21             07 10' PIPE                    19.2             S5.5      12.7            18.6 814  7.28           6.17       1.39 4.64            1.99
                                            2W        3.27      .70  2.27           .29        1.28             M                              19.1             60.6      11.4            20.3 a."  8.36           6.50       3.73 5.11            2.06
                                            220       3.59      .83  2.44           .34        1.40             .08 .90        01              21.0             72.4      14.7            24.9 9,55 10.0           7 14       445  S.62            2.44
                                            240       3.92
                                                                .96  2.67           .41        1.51             .10 go         '01             22.9             911.5     16.1            28.7 10.4 11.5           7.79       5.22 6.1)            2.91  1
                                            260       4.25 1.13      2.39           47         1.66             .12 1.06       .04             24.9             99.2      17.4            33.0 11.3 13.7           8.44       6.07 6.64            3.29
                                            280       4.50 1.30      3.11           14         1.79             .13 1.15       04                                         19.5            38.1 12.2 15.7           909        6-9S 7.15            1.85
                                            300       4.901 1.411    3.33           .62        1.91             115 1.22       @OS                                        20.1            41.2 11.0 17.9           9.74       790  7.66            4.37
                                            120       5.11 1.66      3.56           .69        2.05             17 1.31        06                                         21.6            46.4 13.9 20.1           10-40      6.96 9.17            4.93
                                            340       S.44 1.97      3.78           76,        2.18             19, 1 19       07, 12*         PIPE                       22.9            54.5 14.6 22.5           11 00      996  &.So            5 50
                                            360       5.77 2AY7      4.00           .86        2.30             Z11147         07 1                                       24 2            60.2 156  24.9           11-70      11.0 9.10            CIS
                                            380       6.19 1.23      4.22           44         2.4)             24155          081 1.08        01                         21.6            66 716,5  27 7           12.1       12.2 9.59            618
                                            400       6.44 2.5       4.41      1.03            2.60             10             1.14            041                        26.8            7Y) 17 4  30.6           13.0       11 4 1010            7-S2
                                            00        7 1.0 3.1      5.00      1.29            Z-92             212SI 1 64     1111128         05                                         19 5      36.7           119        167  11.49           9.31
                                            500       S02 18         5@ 56     1.36            3,19             391 104        111 1 42        051                                        21 7      461            16.2       20,1112 6            11.1
                                            550       &.92 4 5       6.11      1.66            3.52             461 1 24       161 1 56        061                                        .219      55,0           17.9       224. 5130            Is 5
                                            000       162 5 3        6-0       Z-19            3.85             14'41          1111 1.70       07                                         26.0      044            19.5       '8.5
                                                                                                                IS             ,
                                            650       10-40 6.2      7.n            3          4.16             612 6          1194            09                                         28.2                     12LI       IN   1116,1400       1151.63
                                                                               2.5
                                                                                                                               199             10                                                                  22.7       179  1760            21. 1
                                                      11.2 7 1       7.78      2.92            4.46             .71 296        14                                                                                  1
                                            750       12.08.1        9.34      3.3S            4.60             al 306         -18 2.13        11                                                                  24.4       0.0  19.90           24@O
                                            am        12.8 9 1       8.90      3.74            5 10             S91 3 26       31 2 27         11                                                                  .260       46.4 20-20           26.0
                                            950       11.6 10.1      9.45      4 21            548              1.011 3 47     IS 2.41         15                                                                  127.6      @4 1 11.4            30.1
                                            900       14.4 11.3    10.0        4.75            5.75             16 @1.6        39 2.56         1                                                                                   22.7            33.4
                                                                                                                I-
                                            )SO       15.2 12.5    IO.S        5.26            6.06             13S ) U        41 2.70         1:
                                            1000      16,0 11.7    11.1        5.66            6.18             1.40 409       46 2.84         19
                                            1100      17,616.4     12.2        6.64            7.03             1.65 449       56 1.13         21
                                            1200      19.61 19.2   13.3        5.04            7.66             1.96 4 9D      66 3 C          27
                                            I )M      208          14.4        8.6             8.30             2.28531        76 )69          11
                                            14M       22.4         15.6        10.6            1.95             1:g9 @6171     908 41-98       37
                                                                                               9                112            10
                                            ISCO      240          16.7        12.0            So               2              26              @42
                                            1600      6            17 9        11.6            0'21             3. 6 11        1.111 54.5s     46
                                                                   M.0                         I                .'91715        1 19            57
                                            Iam                                                11'50            4 1)           11
                                            2=1                    22.2                        12.78            5              569             70
                                            2200                   24 4                        1405             6              6.2S            ss_
                                            2400                   226-7                       15-32            6.7 980        2.37 681
                                            2600                                                                10.61          2.73 38
                                                                                                                                               14
                                                                                                                11.41          3 15 7.95       1.29
                                            3000                                                                12.24          3.58 8 52       1.48
                                            32M                                                i                IVOS           3.7 9.10        L.65
                                            35M                                                                 14 )0          4 74 9.95       1.98
                                                                                                                               7               1.




                                                                                                                                               96
                                            38CO                                                                11S.51         6.3 10.60       2.30,
                                            4=                                                                                 11.92           2.76
                                            45W                                                                                12.74           3.24
                                                                                                                               14.20           3.9S
                                            5500                                                                                                                                                                                                    34
                                            awo
                                   "Datis             shown is coiculated                      from Williams and               Hazen formula H                  3.023                     V1.852                   gC - 150.  For -ater at
                                                                                                                                                                C 1.852 ()                1.167
                                   60"F,              Whatit H     hood loss, V = fluid velocity ft./soc.. D = diameter of pipe, it,
                                   C z cooilicient representing roughness of pipe interior surface.










                                         CHART 2A.



                                         TM
                             "PERC-RITE    FILTER UNIT LOSSES




                  TOTAL ABSORPTION                      TOTAL LOSS
                   FIELD FLOW GPM                         IN PSI


                          5                                2.00


                          6                                2.00


                          7                                2.00


                          8                                2.50


                          9                                3.00


                         10                                3.45


                         11                                3.95


                         12                                4.80


                         13                                5.08


                         14                                5.75


                         15                                6.85


                         16                                8.40


                         17                                9.40


                         18                               10.35


                         19                               11.80


                         20                               12.25


                         21                               14.15


                         22                               15.30


                         23                               17.00


                         24                               18.35


                         25                               20.25



                                                                              35









                                          CHART 3A.

                     "PERC-RITE ,Tm DRIPPER LINE PRESSURE REQUIREMENTS
            (Shown in 10 Feet Increments     Round to Nearest Multiple of Ten)

             DRIPPER LINE     PRESSURE PSI        DRIPPER LINE    PRESSURE PSI
              LATERAL LGTH    REQUIREMENTS        LATERAL LGTH    REQUIREMENTS


                   50 FEET         7.0                280 FEET         13.5


                   60              7.0                290              14.3


                   70              7.0                300              15.2


                   80              7.0                310              16.0


                   90              7.0                320              16.9


                  100              7.0                330              17.9


                  110              7.0                340              18.9


                  120              .7.0               350              19.9


                  130              7.0                360              20.9


                  140              7.0                370              22.0


                  150              7.0                380              23.1


                  160              7.0                390              24.2


                  170              7.0                400              25.4


                  180              7.0                410              26.6


                  190              7.4                420              27.9


                  200              8.0                430              29.2


                  210              8.6                440              30.5


                  220              9.2                450              31.9


                  230              9.9                460              33.3


                  240             10.5                470              34.7


                  250             11.2                480              36.2


                  260             12.0                490              37.7

                  270             12.7                500              39.3



                                                                               36








                                           CHART 4A.
                                   PUMP PERFORMANCE CHARTS


              PUMP      MOTOR    DISCHARGE SUCTION LIFT & PUMP CAPACITY (GPM)
              MODEL     HORSE- PRESSURE                -
              NUMBER    POWER        PSI         51    10,    15'     20'     251


                                     30       15.25 13.5     12.0     9.5     7.4

              5 HS       1/2         40       14.4    12.8   11.75    9.4     7.3

                                     50        9.0     8.3    7.0     6.0     5.5


                                     20       17.7    14.8   12.7     9.8     7.3
              OJS-50
                                     30       16.4    14.5   12.7     9.8     7.3
                STD.     1/2
                W-20                 40        9--6    8._8   8.0     6.8     5.3
                PUMP
                                     50        4.7     3.8    2.8     1.5     ---


                                     20       21.5    19.0   17.1    12.8     9.1


                                     30       21.5    18.8   17.1    12.8     9.1
              OJS-75     3/4
                                     40       15.2    13.8   12.8    10.9     8.5


                                     50        8.0     6.6    5.6     3.5     1.1


                                     20       23.4    20.3   18.8    14.3     10.7


                                     30       23.4    20.1   18.7    14.3     10.7
              OJS-160     1
                                     40       20.8    15.8   14.8    12.4     9.4


                                     50       10.3     7.8    6.8     4.1     1.3


                                     20       17.1    16.0   14.1    11.5     8.3


                                     30       17.1    16.0   14.1    11.5     8.3
              JS-7       3/4         40       15.0    14.1   12.6    11.5     8.3

                                     50       10.0    9.25   7.75     6.5     5.1


                                     20       20.5    18.0   15.5    12.5     9.3


                                     30       20.5    18.0   15.5    12.5     9.3
              is-10       1
                                     40       20.3    17.8   15.3    12.5     9.3
                                     50       19.5    17.5   14.3  1 12.1     8.6
           Note: Electrical service     requirements in Part 5 of    this manual
                   (all require 220/230 volt service).


                                                                                 37









           Checkina.Design PmW Size

                 Once your "Perc-Rite  1, TM System design has been calculated and
           all pressure/head losses and requirements have been determined for
           each of the system components you will then add all the pressure
           requirements together to a total required pressure for your "Perc-
           Rite"'rm System.    This is done as described in the summary of
           calculations section.


                 Now use Chart 4A to determine pump size requirement or to
           decide if you may need to make any "Perc-Rite        11Tm design layout
           changes to work within a particular performance capability of your
           pump size. Chart 4A is very simple to use.

                 After you have determined the total operating pressure
           requirement of the "Perc-Rite     11 TM System design, find the model
           number of the "Perc-Rite   11 TM pump you are- using or you may check
           against the standard pump. The Model OJS-50 is the standard pump
           for W-20 models.     Use the discharge pressure line for that pump
           model which is shown on the chart in 10 psi increments. You should
           always round.up to the nearest increment of ten. If the operating
           pressure requirement of your system has been determined to be 27
           psi, then use the 30 psi discharge pressure column to determine the
           qapacity of your pump.        You will then follow that discharge
           pressure column over to the column under the suction lift capacity
           which corresponds to the suction lift measured in feet for your
           system design. As discussed earlier in the suction lift section of
           calculating pressure losses, you will have rounded this number up
           to the nearest multiple of 5.      This will then correspond to the
           suction lift columns in Chart 4A.       The number in the box which
           corresponds to both the discharge pressure and the suction lift for
           that model pump will be the pumping capacity of that pump in
           gallons per minute.

                 You will have already calculated the total operating flow
           required for your "Perc-Rite      11TM System design as discussed
           previously in this design manual. Compare the total operating flow
           requirement of your "Perc-Rite    , TM System design against the pump
           capacity found for your pump model in Chart 4A. The pump capacity
           as f ound in Chart 4A must be equal to or greater than the total
           flow requirement for your "Perc-Rite   1, TM System design. If Chart 4A
           has indicated the capacity of your pump is equal to or greater than
           your flow requirement then you are assured your design is correct
           to assure proper functioning and dosing of your "Perc-Rite           11 TM
           System.

                 Example:   The total operating pressure requirement of the
           "Perc-Rite" TM System is 41.5 psi based on calculations summarized
           in the previous section of this manual.

                 The suction lift is 10 feet based on calculations summarized
           in the previous section of this manual.

                                                                                 38









                The OJS-50 standard pump is used for comparison.       Chart 4A
           shows the OJS-50 at 41.5 psi discharge pressure and 10 feet suction
           lift to have a capacity of 8.8 GPM (since 43 psi is considerably
           less than the 50 psi column in Chart 4A, we may use 40 psi.)

                You have previously calculated the total operating flow of
           your "Perc-Rite  IT' design as shown in previous sections.         The
           previous example has shown a system with 2,000 linear feet of
           dripper line with an operating flow of 18 GPM. Therefore, for this
           system design the capacity of the standard OJS-50 pump, at 43 psi
           and 10 feet lift and 8.8 GPM capacity as shown in Chart 4A, will
           not be sufficient.     The OJS-50 will be 9. 2 GPM short of the
           requirement. (18 GPM - 8.8 GPM = 9.2 GPM) Had the pump capacity
           been equal to or greater than the 18 GPM total flow requirement of
           the system, then your design is correct,using the standard OJS-50
           pump.   You could then proceed with specifying this design and
           proceeding with the installation. This would be a simple layout of
           the drip absorption field in which you have already designed and
           calculated, without any modifications to the standard "Perc-Rite   11 TI
           W-20 unit, as shown in Figure 9 (see Page 52).


           Desian modifications to meet Performance Specifications

                This section will outline and discuss some of the          design
           modification options available in order to accommodate. pump    and/or
           absorption field performance requirements..

           PIM SpecificatiQns and Modifications

                When it has been determined that a specific "Perc-Rite        11 TM
           design has a total flow requirement and pressure requirement that
           exceeds the performance Chart 4A for any one of the available pumps
           you have chosen, you may change your pump specification to another
           model number that may meet the performance requirements of your
           system design.    This is very of ten one of the easiest ways to
           modify a standard system.

                Example:   Meeting design requirements by specification of
           different pumps.    Using the previous example of a 2, 000 feet
           absorption field requiring 18 GPM at a 43 psi calculated pressure
           requirement at 10 feet suction lift, take these requirement numbers
           to Chart 4A.   You will find that no available "Perc-Rite,IT" pump
           will supply the necessary pump capacity flow of 18 GPM at 40 psi
           and 10 feet of suction lift.

                So other design modifications will be necessary-to meet the
           performance requirements of this "Perc-Rite     IITM System.     These
           modifications are discussed in the next section.

                First let us look at two more pump requirement situations

                                                                              39








           using Chart 4A to size the "Perc-Rite"' pump correctly.

                 1., Assume a system design requires a total operating flow of
           13.5 GPM and a 29 psi pressure requirement and a 10 feet suction
           lift.    Compare this to Chart 4A for the standard OJS-50 pump.
           (Since requirement is 29 psi, we will use 30 psi on the chart. ) At
           @30 psi, the OJS-50 standard pump will supply 14.5 GPM at 10 feet
           suction lift.      This pump meets the 13.5 GPM operating flow
           requirement of the "Perc-Rite     11 TM System design.   Theref ore, no
           design modifications are necessary.

                 2. Assume a system design requires a total operating flow of
           18 GPM and a 30 psi pressure requirement and a 10 feet suction lift
           according to all calculations done according to this manual.
           Therefore, looking at Chart 4A, the standard OJS-50 pump falls
           short of 18 GPM by 3.5 GPM.       However, by specifying the OJS-75
           pump, you will be able to deliver 18.8 GPM at 30 psi at 10 feet of
           lift. Therefore, you may proceed with the design by changing the
           standard pump and specifying the 3/4 horsepower OJS-75 pump.

                 Please Note: If your system design can not be modified by any
           modification means discussed in this section. to match the
           performance capabilities of any pump shown on Chart 4A, call Waste
           Water Systems, Inc. at 1-800-828-9045 for pump specification and
           design.


           Modification of Design Layout

                 (Multiple Zone Absorption Fields)

                 Other than changing pump specifications, the most likely
           method of meeting the performance requirements of your "Perc-Rite"     TM
           System design will be to split your absorption field into two zones
           that field flush separately, thus reducing the pressure and flow
           requirements of the system. Another alternative in systems that
           also require large pump capacities when dosing the absorption field
           for waste water disposal is to design the absorption field zones to
           dose and flush separately to adequately reduce your flow and
           pressure requirements. You will often encounter situations that
           will require either separate field flushing or separate field
           dosing "n flushing to meet performance requirements.

                 Example: Separate field flushing

                 Let us assume a system design that requires 3,800 square feet
           of absorption area using 1,900 linear feet of dripper line. This
           system will require 9.7 GPM while dosing the absorption field.

                 Let us also assume all of your design has called for six
           dripper line connections to the flush manifold after running your
           laterals or loops on the contours. This system will require 9.6

                                                                                 40









           GPM for flushing. Therefore, your total operating flow requirement
           is 9.6 + 9.7 = 19.3 GPM.

                Let us assume your pressure requirement calculations show that
           the system will require 40 psi. (All the methods for calculating
           these pressure requirements have been described in previous
           sections of this manual. ) Your suction lift has been determined to
           be 10 feet. Chart 4A shows that at 19.3 GPM and 40 psi and 10 feet
           of suction lif t that there is not an available pump meeting the
           flow requirements of this design. However, by using two zones to
           flush   the  absorption field separately,       you   will  do the
           following:

                Let us say you have two equally sized zones that flush
           independently. Each zone will then have three dripper line flush
           connections at 1.6 GPM each.        Therefore, the flushing flow
           requirement is then reduced to 3 x 1.6 = 4.8 GPM; therefore, 4.8 +
           9.78 GPM (the absorption field dosing flow) would then be an
           operating total flow requirement of 14.5 GPM instead of the
           original 19.3 GPM when using a single zone.           Therefore, by
           recalculating pressure requirements at this reduced f low, the total
           pressure required will.also drop to approximately 33 psi. Now at
           33 psi or even as high as 40 psi, with 10 feet of suction lift and
           14.5 GPM flow requirement the OJS-75 3/4 horsepower will operate
           this system with separate flush zones. For an example layout, see
           Diagram in Figure 10 (see Page 53).     Be sure when designing and
           ordering a "Perc-Rite""' unit for the two zone flushing, you specify
           it to be programmed for that function as it will require special
           assembly and one extra field control valve. You will also notice
           in Figure 10 that two check valves will be required in each return
           flush line before reaching the common return pipe.       This is to
           insure that while flushing each zone flushes separately by stopping
           any back flow of flush water into the other zone (PVC flapper type
           check valves).

                Example: Separate flushing and absorption field dosing.

                Let us assume a system design that requires a total of 6,000
           square feet of disposal area using 3,000 linear feet of dripper
           tubing in the absorption field. This system will require 15.25 GPM
           while dosing a 3,000 linear feet absorption field.

                Let us assume your design has allowed for eight dripper line
           connections to the return flush manifold. (Each lateral loop will
           be less than 400 feet long.) 8 x 1.6 GPM = 12.8 GPM Therefore,
           this design calls for 12.8 GPM to flush the entire absorption
           field. Your total operating flow is then 12.8 + 15.25 = 28.05 GPM.
           Upon reviewing all the pressure requirement calculations, you can
           tell that the total flow exceeds the "Perc-Rite       , TM W-20 Model
           capabilities at 28.05 GPM.    Therefore, you can already plan for
           this design to be a two zone system. (The limits of the pump Chart
           4A and the filter unit Chart 2A do not even reach 28 GPM.) Now

                                                                              41







           design this as a two zone system with separate flush and field
           dosing.   Let us assume we can divide the system into two- equal
           zones of 1,500 linear feet each. Therefore, your total operating
           flow per zone is now 7.6 GPM dosing and four connections to flush
           line x 1.6 GPM (6.4 GPM) for a total of 14 GPM per zone. At 14 GPM
           it is now within the performance of the "Perc-Rite,,TI System. You
           can now continue with your design and specifications by using a two
           zone system. A diagram of a two zone system is shown in Figure 10
           (see Page 53) and Figure 11 (see Page 54).      (Some examples of a
           complete design computation for, two zone systems will be shown
           later in this manual for your reference.)'


           Design of Unequally Sized Absorption Fields

                Because of site limitations it maybecome necessary to layout
           the absorption field design for the "Perc-Rite        , TM System in
           unequally sized areas. The considerations required when doing this
           are discussed in this section.



           Unequally Sized Absorption Fields Dosed as One Zone

                When an absorption field has been designed in two or more
           unequally sized areas but these areas are dosed by a single line
           (dosed at the same time) as shown in the diagram in Figure 9 (see
           Page 52), no special considerations will need to be addressed for
           this type of design.    Since all the absorption field zones are
           being dosed at the same time, each zone will only accept the amount
           of waste water from that dosing cycle that it was designed to
           receive. This is because the flow rate for a smaller zone will be
           proportionally less than the larger zone.      Also unequally sized
           zones or absorption fields that have been designed to flush
           separately but still dose via a single supply line at the same time
           will not need any special considerations in these designs, since
           only the field flushing is done separately, these fields will be
           dosed at the same time; thereby receiving the amount of waste water
           from the dosing cycle it was designed to receive.


           Uneaually Sized Absorption Zones Dosed Separate-1-y-

                When it becomes necessary to design a "Perc-Rite , TM System that
           doses two absorption fields of unequal size separately, it is in
           order to stay within the performance characteristics you desire
           with larger sized absorption fields. Therefore, when a system has
           been designed and laid out in this fashion your concerns that the
           system will mechanically perform correctly have already been
           addressed, you have done all your calculations to be sure of that.
           However,. there is a second concern: dosing the separate absorption
           syatems correctly.    Since you are not going to. dose the entire
           system at the same time but in two separate zones, you will need to

                                                                              42









          be sure that each separate field area receives the correct amount
          of waste water and will stay within the loading rate limits you
          have established in your design. Each zone will have a different
          flow rate while dosing since they have different amounts of dripper
          line in them and different size absorption areas; therefore, they
          can not be dosed equal amounts of water.       For example, if you
          design a single dose at 50 gallons and one absorption field zone is
          1/3 smaller in size than the other absorption field zone then the
          amount of water that is dosed to that zone should be 1/3 less or
          about 33 gallons. If the amount dosed is the same for each field
          of unequal size then the smaller field will receive more than its
          share of the total daily flow that it was designed to handle.

               Achieving equal dosing to different sized absorption fields
          that dose independently is made simple by using the "Perc-Rite   11 TM
          System. The "Perc-Rite"Tm System controller has the capability to
          do this. This is one of the major improvements in the "Perc-Rite 11 TM
          System over all types of conventional systems.


          Time Operated Dosing

               Time dosing for waste water disposal is a major factor in
          contributing to keeping a soil absorption system functioning
          properly. It has already been proven that dosing cycles throughout
          a 24 hour period to dispose of waste water in a soil absorption
          system is the best way to keep the soil from over-saturation and
          soil clogging or failure.         The instantaneous waste water
          application rate of the system should not exceed the water
          absorption capacity of the surrounding soil, to guard against
          surfacing or ponding of the effluent.        This is difficult to
          calculate and achieve because water is applied at discrete points
          throughout the drip absorption field, so even if the total
          application rate is low, water could surface at some locations of
          the field. In all cases the gross application rate should be kept
         .below the soil absorption rate.    Dosing the absorption field in
          pulses instead of continuously or  on demand as waste water flows
          into the dosing tank will help to avoid the over saturation
          problem. This is especially important when the design application
          rate is the same as the soil absorption rate. The instantaneous
          absorption capability of the surrounding soil varies with time.
          The absorption rate will normally be high at the beginning of the
          dosing cycle, before the surrounding soil saturates, then it
          gradually will reduce.       By dosing in timed cycles with a
          predetermined amount of effluent waste water and then resting the
          soil absorption field you will keep the absorption rate of the
          surrounding soil at a higher value and-reduce the risk of failure
          (ponding, surfacing, etc.).

               It has been established that a very good guideline to follow
          in dosing absorption fields is to distribute the total daily waste
          water flow in six equal doses over a 24 hour period. This is not

                                                                           43







           difficult using the "Perc-Rite"Tm System, even with unequally sized
           absorption fields that separately dose.


           How to Set U  R Dosing with the "Perc-Rit

                 The set up of time dosing with a predetermined amount of waste
           water is a simple function of total daily flow divided by the
           number of doses per day and the flow rate of your absorption field.

                 Example of Time Dosing Fields that Supply at the Same Time:

                 Since a single absorption field or multiple absorption field
           zones that dose at the same time and not separately do not require
           special considerations to insure equal dosing, the formula to set
           up dosing is as follows:

                 Amount of daily waste water flow
                 --------------------------------      Amount of Each Dose
                     Number of Doses per Day

                 Assumea 360 gallons waste water flow:

                   360 GPD
                 -----------       60 Gallons per Dose
                   Doses/Day

                 Important: Always order dose amounts in one gallon increments
           not in fractions.

                 Example:    A calculated dose of 58.5 gallons should be
           programmed as 59 gallons.

                 The "Perc-Rite  , TI controller will then be programmed to dose
           every 4 hours (6 times per day) at 60 gallons per dose. All "Perc-
           Rite"Tm controllers are preset at the factory to dose every 4 hours
           since it has been established that this is a good guideline to dose
           and rest soils. So then the only variable that will be programmed
           into any "Perc-Rite   , TM System of this type will be the amount of
           each dose in gallons. The system designer will designate this dose
           amount to the "Perc-Rite  , Tm dealer or manufacturer before the system
           is shipped to the jobsite.       As in the above example f or a 360
           gallon per day system dosing the f ields at the same time, you would
           specify a 60 gallon dosing cycle every 4 hours.


           Ex=ple of Dosing Separate Fields of Egual Size

                 Dosing separate fields of equal size is basically the same as
           in single dosed fields. However, it must be decided if both f ields
           will dose in the same 4 hour time cycle or in separate 4 hour time
           cycles. This probably will be a factor of the dosing flow rate of

                                                                                 44









           each f ield and the amount of time each cycle will run.       Let us
           assume we have two equal fields with 1,100 linear feet of dripper
           line in each field. The flow rate for each field while dosing is
           5.6 GPM or:

                 1,100                                 336
                 ----- = 550 Emitters x .61     336   -----      5.6 GPM
                   2                                    60

           The daily flow of this system is 360 gallons in 6 doses at 60
           gallons each dose. Therefore, at 5.6 GPM per field, one field of
           5.6 GPM will run approximately 10.7 minutes then in this example,
           the first of the equal absorption fields will dose 60 gallons in
           approximately 10.7 minutes and 4 hours later the next equal size
           field will dose for 10.7 minutes. Then another 4 hours later, the
           first field will dose again and so.on. This scenario is favorable
           in that each field will be "at rest" for-8 hours between doses.


                 Important:   Always try to keep each 4 hour dosing cycle a
           minimum of 6 minutes and a maximum of 12 minutes each.



           Exanle of Ecrual Sized Fields Dosing Separate

                 450 GPD Flow with two equal fields of 1,200 L.F. each

                 1,200 L.F.                                   366
                 ---- 2----- = 600 Emitters x .61 GPH = 366 7 60 -- = 6.1 GPM

                 6.1 GPM Field Dosing Flow

                 450 GPD                        75 Gallons
                 ------- = 75 Gallons per Dose  ---------- = 12.2 Min. per.Dose
                 6 Doses                         6.1 GPM     in Each Field Sep.

                 In this case, it would be prudent to reduce the dose time to
           be under 12 minutes by dosing as follows:

                 Order the "Perc-Rite"' unit to dose both fields at each 4 hour
           cycle to distribute the total 75 gallons.      Each field will then
           dose approximately 38 gallons separately but during the same time
           cycle. Therefore, each dose cycle will dose each field as follows:
           38.0 gallons at 6.1 GPM = 6.1 minutes each field during same dose
           cycle. After 4 hours the next dose cycle will be the same. Dosing
           each field separately to dispose of the desired 75 gallons per dose
           each and every 4 hour cycle.


           Dosing Unequal AbsorRtion Fields SeRaraj&jy

                 A little more calculation is required to set up the dosing on

                                                                              45









           unequally sized absorption f ields that dose separately. Since each
           absorption field is unequal in size, each field will have a
           different flow rate while dosing and a different amount of the
           daily flow to be attributed to disposal in that particular field or
           zone.    Therefore, when your daily flow has been calculated and
           established for that particular system, it must be divided
           proportionately to each field that doses separately according to
           size.


                 Example: 450 Gallons per Day flow with two separately dosed
           fields of 1,100 linear feet and 700 linear feet each. Divide the
           daily flow proportionately as follows:

                 To find what percentage of the daily flow will go to each zone
           you will need to know the ratio of difference between each field
           size. The formula to do so is as follows:      Take the number in feet
           of the total in either field one (1,100 feet) or field two (700
           feet) and divide that number by the total footage amount in both
           fields. That will tell you what percentage of the daily flow will
           need to be dosed to that particular field.

                 Field One:


                 1,100 Linear Feet
                 -----------------      .61 or 61%
                 1,800 L.F. (both fields)

                 61% of the total daily flow of 450 gallons will be dosed to
           Field One.

                 450 gallons x .61 = 275 gallons.

                 The remaining amount of daily flow will go to Field Two.

                 Total Flow             450 Gallons per Day or 100%
                 Field One Flow       - 275 Gallons per Day or 61%
                                       ---------------------------
                 Field Two Flow         175 Gallons per Day or 39%

                 We have now established that in this example the 450 gallons
           per day will be dosed as follows:,

                 Field One       1,100 Linear Feet          275 Gallons per Day
                 Field Two         700 Linear Feet          175 Gallons per Day

                 The next step will be to determine whether each field will be
           dosed during the same 4 hour dosing cycle or every other 4 hour
           dosing cycle (which allows each field to rest 8 hours).               To
           determine this you must calculate the dosing flow rate for each
           field.




                                                                                 46









                      1, 100 L. F.                             335
           Field One  ----------  = 550 Emitters x .61 = 335  ------ = 5.6 GPM
                           2                                  60 Min.


                       700 L.F.                                214
           Field Two  ----------  = 350 Emitters x .61 = 214  ------ = 3.6 GPM
                           2                                  60 Min.


                Therefore,

                       275 GPD
           Field One  ---------  = 49.1 Minutes   Dosing   Time Required
                       5.6 GPM


                       175 GPD
           Field Two  ---------  = 48.6 Minutes   Dosing Time  Required
                       3.6 GPM


                We have now established the total dosing time necessary per
           day for each field to dispose of the daily flow equally. We also
           know we have a maximum of 6 doses per day and a minimum of 3 doses
           per day per field if each field doses on separate 4 hour cycles.
           We also know that we wish to keep each dosing cycle between 6 and
           12 minutes. Both Field One and Field Two should be dosed 6 times
           per day to stay under 12 minutes per dose.

                      49.1 Minutes
           Field One  ------------  = 8.2 Minutes
                         6 Doses


                      48.6 Minutes
           Field Two  ------------  = 8.1 Minutes
                         6 Doses

                Therefore, this "Perc-Rite , TM System with unequal fields dosing
           separately should be ordered with both f ields dosing . during the
           same time cycle every 4 hours. Field One will dose 46 gallons in
           approximately 8.2 minutes then Field Two will dose separately but
           during the same dosing cycle (every 4 hours) 30 gallons in
           approximately 8.1 minutes.

                As you can see, if each field were not dosed at every 4 hour
           dosing cycle, then each field will have only three dosing cycles
           per day.   Field One would run f or over 16 minutes per dose and
           Field Two would run for over 16 minutes per dose.

                In some cases with larger f ields and higher f low rates, you
           may be able to dose the unequal size f ields at separate dosing
           cycles or every 8 hours (3 doses per field) because the increased
           f low rate for a larger f ield will keep your run time under 12
           minutes per field. Below is another example.


                                                                             47









            Dosing Unequal Absorption Fields Separately (cont.)

                  Example:. Assume a daily f low rate of 400 GPD. A low loading
            rate system has required you to design two separate fields. Field
            One has 1,500 linear feet of dripper line and Field Two has 2,000
            linear feet of dripper line. To determine the proportional daily
            flow to each field is as follows:

                  A total of 400 GPD daily flow. The percentage to the larger
            field would then be calculated as:


                  2,000 Linear Feet
                  -----------------  = .57 or 57%
                  3,500 Linear Feet

                  Therefore, 57% of the total flow will go to Field Two which
            has 2, 000 linear feet of dripper line. Field One, which has 1, 500
            linear feet, would be dosed the remaining flow of 43%.

                  400 GPD x .57 = 228 Gallons per Day

                  Therefore, 228 Gallons per Day to Field Two and 172 Gallons
            per Day to Field One.

                  Determine the flow rates during dosing:

                        1,500 L.F.                                 458
            Field One   ---- 2 ----- = 750 Emitters x .61 = 458   60-Min.   7.6 GPM

                       2,000 L.F.                                  610
            Field Two   ---------- = 1, 000 Emitters x .61 = 610 ------  = 10.2 GPM
                           2                                      60 Min.

                  Determine the dosing time required:

                         172 GPD
            Field One   ---------  = 22.6 Minutes per Day
                         7.6 GPM


                         228 GPD
            Field Two   ---------  = 22.3 Minutes per Day
                        10.2 GPM


                  In this case, Field One will need to run 22.6 minutes per day
            and Field Two will need to run 22.3 minutes per day. This "Perc-
            Rite 1, TM System may be ordered to dose each f ield separately at
            separate 4 hour dosing cycles, allowing for 8 hour "rest" between
            field dosing.




                                                                                  48










                 22.6 Minutes                      22.3 Minutes
                 ------------      7.5 Minutes     ------------      7.4 Minutes
                 3 Doses/Day                       3 Doses/Day

                 Even though each field doses on  separate 4 hour cycles only 3
           times each per day, the run time is well within the 6 to 12 minute
           recommended run time range per cycle.


           Dosing Volume and Pimp Float Switch

                 Af ter the maximum dosing volume that will be necessary f or any
           dosing cycle has been determined, your design should also include
           the minimum depth of draw down in your dosing tank.       This depth
           should provide a volume of waste water that is equal to or greater
           than the maximum amount necessary for each dosing cycle.
           Therefore, you will need to know the volume of water per inch in
           depth of the dosing tank intended for use in your design.

                 Example: Suppose your standard 1,000 gallon dosing tank has
           a volume of 15 gallons per inch of water depth       Assume you have
           two fields that dose separately and the larger field requires at
           least 60 gallons per dosing cycle. Therefore, your float switch
           must be set with enough tether or swing length to pull down 4" of
           water so:
                        60 gallon dose
                       ------------------     411
                      15 gallon per inch

                 All "Perc-RiteIITI pump float switches will allow for an even
           ratio of 1" draw down for every 1" of tether length. Therefore, in
           this situation you should allow at least 4 inch of swing length in
           the float switch tether.

                 Another Example:   Dosing tank with 10 gallons per inch of
           water depth. Dosing volume required per dose is 50 gallons.

                        50 gallon dose
                      -------------------      511
                     10 gallons per inch

                 So set the float switch with 5 inch of swing.

                 Note:  You may wish to always set the f loat switch with an
           extra inch or so swing. the extra volume allowed will not upset
           the dosing balance of your "Perc-Rite   ,TM System as the system will
           be set to only dose the amount specified for each field.







                                                                               49









           Summary

                Time dosing of the "Perc-Rite  IT' Drip Soil Absorption System
           is an integral part of each individual system design. Some designs
           such as multiple absorption field designs and separate dosing
           absorption fields will require more calculations than other "Perc-
           Rite IITm designs. The method of calculations to determine these
           dosing variables have been described in this section. The variable
           time and flow dosing capability of each individual "Perc-Rite    I, TM
           System is one of the advantages of using such a system for a long
           term soil absorption system.


           "Perc-Rite" m Designs on Sloping Ground

                As described previously, the pressure compensating type
           dripper line used in the "Perc-Rite  ,TM Waste Water Disposal System
           provides for even drip emission rates throughout a broad range of
           pressure differences.    The problem with most pressurized soil
           absorption systems is, on sloping ground the pressure differences
           caused by head losses in the vertical lift of such systems would
           cause problems in providing equal effluent distribution.       Since
           these head losses do not effect the "Perc-Rite   , TM Systems dripper
           discharge rates, no special design considerations will need to be
           calculated. Simply follow the guidelines for determining pressure
           requirements as described previously in this manual. As long as
           you design within those performance standards, no additional
           eleva:tion change head losses will need to be calculated. This is
           another advantage "Perc-Rite 11 TM Systems have over other conventional
           pressure systems or non-pressure compensating turbulent flow type
           drip systems.

                When designing "Perc-Rite 11 TM Systems on severe slopes of 20%
           or more because of installation difficulties and excess
           gravitational pull on the effluent down hill it may be advantageous
           to separate the dripper line laterals runs to 36 inches separation
           instead of the normal 24 inches separation. This can be a design
           decision, or based on soil scientist recommendation and personal
           preference based on any difficulties that may be encountered
           installing laterals as close as 24 inches apart on severe slopes.
           In very poor soils with slow absorption rates, you may increase
           absorption field sizing when separating the dripper laterals to 36
           inches apart.    This is to assure that you do not exceed the
           instantaneous loading rate capabilities of that particular soil,
           because you have increased the run time of each dose by using less
           dripper line in the absorption area required by your design.
           Remember that all lateral lines must be placed on the ground
           contours to keep each lateral dripper line as close to level as
           possible.   When making loops or turns with connections to the
           supply line, always use solid tubing, not dripper line, in the
           turns as described and shown previously in this manual. When you
           make a turn to the next elevation, you may even wish to raise the

                                                                             50








              solid tubing in your loop or turn over an earthen dam. This will
              ensure that the water from the upper lateral dripper line will not
              f ollow the solid tubing down to the next lower lateral line, see
             .Diagram below.










                                                                                W




                             ORIPPER UNE


                                                                                           W


                    FINISHED GRADE                                                    \jP






                                                                           V








                                                                                                         Ilk
        PVC PIPE

                 PVC




                             EARTHEN DAM IN TRENCH
                             TO PREVENT FLOW ALONG
                             FLEX PVC






                               SECnON - DRIIPPER UNE TO FU=W CONFOURS
                                  PVC MANIFOLD PEWeC=LAN TO GRAIDE














                                                                                                       51









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                                     FIGURE 10
                                SEPAF44TE SUPPLY AND COMMON RETURN
                                W/ CHM VALva ALWWWX INC)MOUAL
                                MUD FLUSHM







                                   WWGE









                                  SAM nAm UNE-


                                              7mriow
                                               TAW

                          FLOAT SWM:H POWER LHM (2)
        SUPPLY LIKE             SUPPLY LANE     TAOW

                                                sucnow LINE
                     4e,  ------- -96 P%c im          -----PVC
                                                      90       qG--f=A FUZW LINE
                                riI




          tat

          46







                                                          IL

                                I "@V47
                11111   fill  I ii         'fill   fill
                   III  fill  I111

                                                                     53
                L.J  LJu   LJ I             u  LJ  LJ LJ

                                                    -FO@C MWIFOLD




                                                 FIGURE 11
                                    SEPARATE SUPPLY AND SEPARATE RETURN LINES


                                                     PRESSURE COMPENSATING DRIPPER LINE
                                                 600 LF. - 2' SPACING - 300' LATERAL RUNS
                          PVC MANIlFDLD
          90 ---so - - - - - - - -
                    c --zzzzzzzzzzzz                  ---

                      -----------------

                                             -----------------------
      Pvc In-)I,                                              --------
                    r-:--__            Fm                                 IZZ_Z----J                 P*lr- M"FOLD
                      ----------------------------------                                  I
                             -- -----------------------------                                *,-P%c 7m



                                                                                                       YEW 0
                                                                                                    minow POINT'






                                                                                                         FLLISH LINE
                                                  HOME



           SUPPLY UNS2                                                            C@ VALVIIS


                                         nor           LIM CIO




                                                                 SLcnl3m LUMNE




                                   -SUPPLY LINE






                                                             FMD FLUSH LINE



                               MANIFOLD
      Pvc 7m---310
                    r- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --      <_@ TEE
           TIM---so - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                    c:::zzz    - - - - - - - - - -  Z -1 - - - - - - - - - - - - - - ---                VEwr 0
                                                               - - - - - - - - - -                   HND*Nr POW

                                                            - - - - - - - - - - - - - - - -  *-FIC TEE
      PVC go      L- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                               z i z zi z       z----z::i z                                          PVC MANIFOLD
                                                                      svzm










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                                       F





























                                                                    - - - - - - - - - - - -   ---- fpvc go

                              PAM PRESSURE COMIMCNLAIM DINIM LINE                                        54
                             1200 L.F. - 2' SPACINC - 4W UMMAL RUNS







 






        EXAMPLE DESIGN CALCULATIONS


         FOR "PERC-RITE" TM SYSTEMS


            USING THIS MANUAL



 










 
 






           Example Design 1: (See Example Worksheet on Page 68)

                Daily Flow.- (Line 2 on Worksheet) A three bedroom house x
           150.GPD/bedroom = 450 GPD

                Loading Rate - Soil reports show Sandy Clay Loam. (Line 3 on
           Worksheet) Chart 1 shows .15 gallons pet square feet per day as a
           loading rate. (Line 4 on Worksheet)

                Total Area Requirement    (Line 5 on Worksheet)

                           450 GPD
                      ----------------    3,000 Sq. Ft.
                      .15 Loading Rate

                Total Dripper Line Required - (Line 7 on Worksheet)

                      3,000 Sq. Ft.
                      -------------- = 1,500 Linear Feet
                      2 Feet Spacing

                Determine Layout and Shape - (Line 13 on Worksheet) Area on
           the lot is approximately 60 feet x 50 feet or 3,000 Sq. Ft. This
           is conducive to five laterals or loops 300 feet long.              (5
           connections to the return flush line.)

                Assumptions:   Distance to drip field is 110 feet (1" PVC).
           Distance from dosing tank to pump is 50 feet (1 1/4" PVC). Suction
           elevation lift is 10 feet.    Return flush line length is 120 feet
           W. PVC).

                Septic tank size - a 1, 000 gallon septic tank (Line 9 on
           Worksheet) and a 1,000 gallon dosing tank (twice the daily flow)
           (Line 10 on Worksheet).

                Depth of Line - (Line 11 on Worksheet) Soils analysis shows
           optimum depth at 18" deep.


           Begin Design

                Dosing Flow Rate - (Line 14a on Worksheet)

                1,500 L.F.                                     457.5
                ----------  = 750 Emitters x .61 GPH = 457.5   ------ = 7.6 GPM
                2' Spacing                                    60 Min.

                7.6 GPM dosing rate

                Field Flush Flow Rate - 5 connections to     the return f lush
           line x 1.6 GPM    8 GPM Flushing Rate (Line 14c   on Worksheet)


                                                                              55








                Total flow requirement 15.6 GPM

             lculate Flow Logs and Pressure Requirement

                A. Suction Line Loss - (Line 15a on Worksheet) Chart 1A is
           1 1/4" at 15.6 GPM = 3.05 Loss per 100 feet.
                                      1.53
                3.05 x .5 = 1.53      ----       .7 psi (Round up to 1 psi)
                                      2.31


                B. Suction Lift       (Line 15a on Worksheet) 10 Vertical feet

                C. Supply Line      (Line 15b on Worksheet) 1" 110 feet long.
           Chart 1A shows 1" PVC at 15.6 GPM = 11.8 per 100 feet.
                                      12.98
                11.8 x 1.1 = 12.98    -----     5.6 psi (Round up to 6 psi)
                                      2.31


                D. Return Flush - (Line 15c    on Worksheet) 1" 120 feet long.
           1" PVC at 8 GPM = 3.68 per 100 feet.
                                      4.41
                3.68 x 1.2 = 4.41     ----     1.9 psi (Round up to 2 psi)
                                      2.31


                E.   Pump Filter Unit - (Line 16 on Worksheet) Chart 2A shows
           15.6 GPM  = 6.85 psi

                F.   Fittings - 0

                G.   Elevation Changes (assume) - (Line 17 on Worksheet)          5
           vertical  feet to the highest point in dripper field

                   5
                ----  = 2.16 psi (Round up to @.2 psi)
                2.31


                H. Dripper Line Laterals - (Line 18 on Worksheet) Chart 3A
           300 feet = 15.2 psi

                Summary:
                A.   Suction.Line - (Line 15a on Worksheet)              1.0   psi
                B.   Suction Lift of 10 feet
                C.   Supply Line - (Line 15b on Worksheet)               6.0   psi
                D.   Return Flush - (Line 15c on Worksheet)              2.0   psi
                E.   Filter Unit - (Line 16 on Worksheet)                6.85  psi
                F.   Fittings                                            0.0   psi
                G.   Elevation Changes - (Line 17 on Worksheet)          2.2   psi
                H.   Dripper Line Laterals    (Line 18 on Worksheet)     15.2  psi
                                                                               ---7
                      Total Pressure Req.    (Line 19 on Worksheet)     33.25  psi



                                                                                 56








           Check Pump PerfoxTaance

                On Chart 4A use 40 psi at 15.6 GPM at 10 feet lift.          The
           standard OJS-50 will not work. The 3/4 horsepower pumps will not
           work. The JS-10 1 horsepower pump will work at this performance
           requirement. It provides 17.8 GPM at 40 psi at 10 feet of lift.
           You could use this design as it is and specify this available pump.
           However, instead of specifying the 1 horsepower pump, you may want
           to make some modifications to your design. For example:

                You may increase the force main supply and return flush line
           size to 1 1/4".    The reduction in supply and return loss brings
           your total pressure requirement down to less than 30 psi. You may
           then specify the OJS-75 or the JS-7 3/4 horsepower pumps.

                In order to use the standard pump and reduce the performance
           requirement even more you may split the field to flush separately.
           By reducing the flushing flow requirement to a maximum of 3
           connections to the flush line in each separate flush zone you will
           now reduce the total flow requirement by 2 connections x 1.6 GPM =
           3.2 GPM.    This will reduce all the pressure, requirements as
           calculated above and you may now use a total f low of 12.4 GPM
           filter unit pressure loss is now down to 5. 0 psi according to Chart
           2A.   Your supply line losses and return line losses will also
           reduce.


                As you can see, all the methods for calculating performance
           requirements may be used to modify any "Perc-Rite"Tm design to meet
           your specific requirements.

                The next step in reducing the performance requirements of this
           system would be to split the absorption field into two zones that
           f lush and dose separately.    This should reduce the pressure and
          .flow requirement significantly.      Let us work through the same
           example after modifying the design into separate field flushing and
           dosing with 1 1/4" supply and return lines.

                Two zones: 900 feet and 600 feet each

                Dosing Flow -

                         900 L.F.                               275
           Field One   ----------   450 Emitters x .61    275  -----   4.57 GPM
                           2                                   60 Min.


                        600 L.F.                                183
           Field Two ----------    300 Emitters x .61    183  ------ = 3.05 GPM
                          2                                   60 Min.


                Flushing Flow       Use Field One, which has 3 flush line
           connections, to determine flush flow 3 x 1.6 - 4.8 GPM.



                                                                               57







                 Total Operating Flow - 4.8 GPM + 4.5 GPM (largest field) = 9.3
            GPM  Total Flow.       Use 9.3 GPM to determine all pressure
            requirements.

                 Pressure Requirements -
                       Suction Line - (Line 15a on Worksheet)              .3   psi
                       Suction Lift of 10 feet
                       Supply Line    (Line 15b on Worksheet)              1.0  psi
                       Return Flush    (Line 15c on Worksheet)             1.0  psi
                       Filter Unit    (Line 16 on Worksheet)               3.0  psi
                       Fittings                                            0.0  psi
                       Elevation Changes - (Line 17 on Worksheet)          2.2  psi
                       Dripper Line Laterals - (Line 18 on Worksheet)      15.2 psi

                       Total Pressure Req. - (Line 19 on Worksheet)       22.7 psi


                 Performance Requirement - For 23 psi at 9.3 GPM and 10 feet
            of lift will now  allow you to use the standard pump which will more
            than supply the required head and pressure.

                 Now let.us  look at dosing. 450 GPD.

                              900 Feet
                 Field One   ----------  = .60 or 60%
                             1,500 Feet

                 Therefore,  Field One gets 60% of total daily flow (450 x .60
              270 GPD)


                 Field One        270 GPD
                 Field  Two       180 GPD


                                  450 GPD


                         270 GPD                          60 Min.
            Field One    --------- = 60 Min Daily         -------   10 Min per Dose
                         4.5 GPM       Dose Time          6 Doses


                         180 GPD                          60 Min.
            Field Two    --------- = 60 Min Daily         -------   10 Min per Dose
                         3.0 GPM       Dose Time          6 Doses

                 Note: By dosing six times per      day or every 4 hours, the 10
            minutes per dose f alls within the recommended 6 to 12 minute dosing
            time.

                 Therefore, order the "Perc-Rite"Tm unit for each separate zone
            to dose in the same 4 hour dose cycle, six times per day.            (45
            gallons for Field One and 30 gallons for Field Two.)



                                                                                  58








           Pj= Float Switch

                Since the dosing volume per cycle will be 45 gallons   in this
           case (largest field) the float switch is to be set as follows:

                Assume a 1,000 gallon dosing tank with 15 gallons volume per
           inch of water depth.

                45 gallons
                ----------    3 inches
                    15

                Specify float switch to be set at a minimum of a 3 inch swing.


           Example Desian 2:

                Daily Flow - (Line 2 on Worksheet) A- four bedroom house x 150
           GPD/bedroom = 600 GPD

                Loading Rate - Soil reports show Clay Soil (Line 3 on
           Worksheet). Lot size allows us to use a .1 gallons per square feet
           per day loading rate (-Line 4 on Worksheet).

                Total Area Requirement    (Line 5 on Worksheet)

                          600 GPD
                     ----------------     6,000 Sq. Ft.
                     .1 Loading Rate

                Total Dripper Line Required - (Line 7 on Worksheet)

                     6,000 Sq. Ft.
                     --------------  = 3,000 Linear Feet
                     2 Feet Spacing

                Determine Layout and Shape - (Line 13 on Worksheet) Assume
           two areas on lot located 4,000 sq. ft. in one area and 2,000 sq.
           ft. in the second area.

                With such a large system design, you should already consider
           this a two zone system.

                Field One is a 4,000 sq. ft. area will allow for 2,000 linear
           feet of dripper line in six laterals or loops, the longest will be
           380 feet.

                Field Two is a 2,000 sq. ft. area will allow for 1,000 linear
           feet with four lateral runs, the longest will be 300 feet.

                Septic tank size - a 1, 500 gallon septic tank (Line 9 on
           Worksheet) and a 1,000 gallon dosing tank (Line 10 on Worksheet).

                                                                              59








                Assumptions: The distance to the dripper field from the unit
           is 100 feet. The distance from the dosing tank to the pump-is 50
           feet. The return flush line distance is 100 feet.

                Since this is a large system with a large flow rate, you can
           already assume we should use larger pipe sizes. Use 1 1/4" for the
           suction, supply line and return flush.


           Begin Design

                Dosing Flow Rate - (Line 14a on Worksheet)

                2,000 L.F.                                    610
           One  ----------   1000 Emitters x .61 GPH   610  -------   10.1 GPM
                21 Spacing                                   60 Min.

                1,000 L.F.                                     305
           Two  ----------   500 Emitters.x .61 GPH   305   -------    5.0 GPM
                21 Spacing                                   60 Min.

                Use 12.7 flow rate in pressure requirement calculations.

                Field Flush Flow Rate - (Line 14c on Worksheet)

                Field One - 6 connections x 1.6 GPM = 9.6 GPM


                Field Two - 4 connections x 1.6 GPM = 6.4 GPM


                Use 9.6 GPM in pressure/flow requirement calculations.

                Total flow requirement 9.6 + 10.1 = 19.7 GPM (Round to 20 GPM)


           Calculate Flow Loss and Pressure ReQMirement

                A. Suction Line Loss - (Line 15a on Worksheet) Chart 1A is
           1 1/4" at 20 GPM = 5.21 Loss per 100 feet.
                                      2.60
                5.21 x .5 = 2.60     ------     1 psi
                                      2.31


                B. Suction Lift     (Line 15a on Worksheet) 5 Vertical feet

                C. Supply Line     (Line 15b on Worksheet) 1 1/4" at 19 GPM.
           Use 5.21 per 100 feet.

                     5.21
                     ------ = 2.2 psi
                     2.31


                D. Return Flush - (Line 15c on Worksheet) 1 1/4" at 9.6 GPM

                                                                              60








           1.44 per 100 feet.

                     1.44
                     ----      .6 psi (Round to 1 psi)
                     2.31

                E.  Pump Filter Unit - (Line 16 on Worksheet) Chart 2A shows
           20 GPM   12.25 psi

                F.  Fittings - 0

                G.  Elevation Changes (assume) - (Line 17 on Worksheet)

                     Elevation rise from pump unit to the highest point in the
           field is 5 feet.


                5 feet
                ------  = 2.16 psi
                  2.31


                H. Dripper Line Laterals - (Line 18 on Worksheet) Chart 3A
           380 feet = 23.1 psi

                Summary:
                A.   Suction Line - (Line 15a on Worksheet)             1.0 psi
                B.   Suction Lift of 5 feet
                C.   Supply Line - (Line 15b on Worksheet)              2.2 psi
                D.   Return Flush - (Line 15c on Worksheet)             1.0 psi
                E.   Filter Unit - (Line 16 on Worksheet)              12.25 psi
                F.   Fittings                                           0.0 psi
                G.   Elevation Changes - (Line 17 on Worksheet)         2.16 psi
                H.   Dripper Line Laterals - (Line 18 on Worksheet)     23.1 psi

                     Total Pressure Req. - (Line 19 on Worksheet)     41.71 psi


           Check PIM Performance

                Chart 4A        11

                Use 40 psi at 5 feet suction lift. The OJS-100 and    the JS-10
           1 horsepower pumps will supply over 20 GPM at 5 f eet of suction
           lift and 40 psi. However, this is the upper limits of the "Perc-
           Rite"Tm W-20 System. when large designs meet this threshold great
           care should be given to the calculations and installations. The
           system has been designed with separate dosing and flushing so
           further performance requirement reductions by anymore design
           changes will be minimal. You may wish to call Waste Water Systems,
           Inc. at 1-800-828-9045 to check on specifying another pump.




                                                                               61








           Tike D

                Field One    2,000 L.F.
                             ----------  = .66
                             3,000 L.F.

                66% of the daily flow is to be dosed to Field One.

                .66 x 600 GPD = 396 gallons per day

                Field Two gets the remaining flow of 204 gallons per day.


           Field Dosing Flows

                Field One 10 GPM
                Field Two 6.4 GPM
                Total Dosing Time per Day

                              396
                Field One    -----      39.6 minutes
                              10


                              204
                Field Two    -----      31.8 minutes
                              6.4

                Six doses per day each field.

                              39.6
                Field One    ------  = 6.6 minutes = 66 gallons
                                 6


                              31.8
                Field Two    ------  = 5.3 minutes = 34 gallons
                                 6

                You should probably order this unit to dose both fields during
           every 4 hour dosing cycle. However, you have the flexibility in
           the "Perc-Rite"" unit to dose one of these zones every other dosing
           time cycle or every 8 hours. This may be desirable in the smaller
           zone which is now running only 5.3 minutes. The field dosing would
           then be as follows:

                Field One - 6 doses per day at 66 gallons or 6.6 minutes per
           dose as shown above.

                Field Two - 3 doses per day (every other dosing cycle) or

                204 gallons
                -----------    68 gallons per dose
                  3 doses


                                                                                62








                 with a run time of 10.6 minutes each dose. This field will
           then dose every 8 hours.

                 So the ideal way to design and order the "Perc-Rite    11 T" in this
           case  would be by dosing zone one 66 gallons per dose, every dosing
           cycle (6 times each day) and dose zone two at 68 gallons per dose
           at every other dosing cycle (8 hours) three times per day.




           Pump Float SwitCh

                 Since the dosing volume per cycle will be 68 gallons in this
           case  (largest field) the float switch is to be set as follows:

                 Assume a 1,000 gallon dosingtank wi     th 15 gallons volume per
           inch  of water depth.

                 68 gallons
                 ----------     4.6 inches
                     15

                 Specify f loat switch to be set at a minimum of a 5 inch swing.


           Designs not Meeting Performance CaRabilities of the "Perc-Rite'-"
           W-20 System

                 In some cases with larger flows and very low soil loading
           rates you will be unable to meet the performance capabilities of
           the "Perc-Rite"T" System as shown in this manual, even by using all
           the design modifications detailed in this manual. This does not
           mean a "Perc-Rite    1 TI System will not work in that particular
           situation. You should call Waste Water-Systems, Inc. at 1-800-828-
           9045 for "Perc-Rite  1, T" Equipment Specifications that will meet those
           performance requirements. Waste Water Systems, Inc. will provide
           a system with modifications to the Standard Available Equipment to
           meet your design specifications, which may include a larger "Perc-
           Rite , Tm Filtration and Pump Unit.












                                                                                  63











           PART FIVE


           Other Specifications and Equipment
           Used in the Complete "Perc-Rite"' System






                All the equipment necessary to complete a "Perc-Rite   11 TI  waste
           Water Disposal System should be included into a single worksheet
           that can be used to be sure the system will be installed as
           designed. The worksheet can also serve as a checklist to be sure
           the design was done correctly and has taken into consideration all
           the required calculations. A sample of a worksheet is shown at the
           end of this section (see Page 68). A copy of this worksheet and an
           accurate sketch of the system design layout including all drainage
           and landscaping requirements should be filled out and drawn up for
           every system designed. Copies of the worksheet and sketch should
           be given to the local health department or regulatory agency.
           These worksheets and sketches are also helpful for the installation
           contractor in making a list of materials necessary.


           Septic Tank and Dosing Tank

                As noted earlier a "Perc-Rite"Tm System has at least two
           separate tanks.   A septic tank and dosing tank or any specified
           pretreatment means such as an aerobic treatment unit with a dosing
           tank are what is usually installed. If the "Perc-Rite   11 TM System is
           being used to replace an existing septic system the existing septic
           tank may be used (after being pumped out and cleaned) and only one
           additional tank will need to be installed.


                The septic tank receives waste water directly from the house.
           It is sized according to state and local regulations for
           conventional systems. The septic tank should be of two-compartment
           desig n for maximum solids retention. It is very important that the
           septic tank and pumping chamber are watertight. One-piece tanks
           are best. When using two-piece tanks, the tongue-in-groove joint
           must be carefully sealed with asphalt rope mastic. This is very
           important. The tanks (especially the dosing tank) must be water
           tiaht.

                Effluent from the two-compartment septic tank flows by gravity
           through a four inch solid PVC pipe to the pumping chamber.        The
           pumping chamber should have a liquid capacity of at least two times
           the daily waste flow from the house and can be a single -compartment


                                                                               64









           design. Dosing tanks may be sized to hold only 24 hours daily flow
           capacity. However, it is beneficialto allow for more storage in
           case of equipment failure or power outage. The dosing tank must be.
           provided with aboveground concrete or masonry (or their equivalent)
           manhole risers to provide easy access for clean-out and pump
           service. The riser should be placed over the primary chamber of
           the septic tank and above the pump access hole in the pumping
           chamber. Risers should be wide enough to accommodate the existing
           lids on the tanks, should extend at least six inches above the
           finished grade of the site and should also be covered with a
           concrete, metal or plastic lid to local specifications.

                Standard well tiles can be used for the risers, provided that
           the inside diameter is larger than the access hole in the tank.
           All joints must be sealed to prevent the infiltration of surface
           runoff and ground water to the tanks.


           Pipes and FittiDga

                All pipe and fittings in a "Perc-Rite 11 TM System should be made
           of PVC plastic.    PVC. is lightweight, easy to use and resists
           corrosion.   All joints must be sealed with an appropriate PVC
           solvent cement. In instances where check valves are necessary, PVC
           flapper type check valves may be used.


           Air Vents

                As discussed previously in this design manual, air vent/vacuum
           breakers are required at the high point of every dripper field or
           zone. Waste Water Systems, Inc. will supply air vents as needed.
           They should be installed in a valve box. Plastic valve boxes of
           any choice are fine. The air vents are fitted with 1/2" male pipe
           threads that fit standard 1/2" female adapters.


           Electrical Ser

                The electrical    requirement   for any W-20     "Perc-Rite"  TM
           residential unit is as follows:

                For any available "Perc-Rite   11TM pump specify a dedicated
           220/230 volt 20 amp service. (3 wire service)


           Home Water Saving Devices

                Any home with a "Perc-Rite"Tm System should minimize the
           hydraulic load on the soil absorption system by using low flow
           water saving devices such as low flow showerheads and low flow
           commodes.   These devices are a simple low cost way of reducing

                                                                             65









           water use without inconveniencing the homeowner.


           Site Preparation Specifications

                One of the most important concerns for a "Perc-Rite"" System
           is to protect the site from soil disturbance by heavy equipment.
           Removal or compaction of the topsoil, especially during wet
                                                                           TM
           weather, may destroy the site's suitability for a "Perc-Rite" .
           As soon as the absorption area has been designated, it should be
           flagged, roped off and "quarantined" from construction traffic. No
           site preparation or LPP construction work should occur if the soil
           is wet. As a rule of thumb, if the soil is too wet to plow, it is
           too wet to disturb for system construction.

                After the location is staked out and the soil is dry enough to
           plow, the site should be cleared of brush and small trees.        if
           larger trees are removed, they should be cut off rather than
           uprooted in order to avoid creating depressions and damaging the
           soil-pore network.

                Provisions must be made for intercepting or diverting surface
           water and shallow ground water away from the absorption area,
           septic tank and pumping chamber.    This can be done with grassy
           swales, open ditches or curtain drains.

                If the site requires imported fill to improve surface
           drainage, it must be incorporated evenly into the underlying
           natural soil. It is very important that no sharp interface remain
           between the natural and imported soil layers. Before applying the
           imported fill to the absorption area, the ground surface must be
           tilled with a small plow or cultivator.    Fill should be applied
           with a minimum of wheeled traffic on the area, and the area tilled
           again to ensure even mixing. A very small tractor should be used
           to spread the material around and to provide a convex shape to the
           area. There should be no low spots or depressions, and the final
           shape should shed, rather than accumulate rainwater. Use of fill
           to supplement the soil profile is discussed in Part 6 of this
           manual.


                After the area has been cleared and shaped, the location of
           the lateral lines and'supply manifold should be accurately staked
           out according to design specifications. Each lateral line should
           be laid out along a contour. One lateral may be higher or lower
           than the next one, but each individual lateral run should follow a
           contour evenly.  In no case should a lateral line be allowed to
           slope away from the manifold in any direction without using earthen
           dams or other measures as shown in the Diagram on Page 12.





                                                                            66









           Final Landscaping

                After a "Perc-Rite 11 TM System has been installed, the following
           should be specified in final landscaping requirements to ensure the
           system will not be overloaded with excess rain water and runoff.

                - The distribution field is shaped to shed rain water and is
                  free of low areas.


                - Curtain drains, grassy swales or ditches for diverting
                  ground and surface water are properly installed.

                - Gutter and downspout drains are directed away from the
                  system.

                Finally, the entire area should be planted with grass in order
           to prevent erosion. The soil should be properly tilled, limed (if
           necessary) and fertilized before planting.       After applying an
           appropriate grass seed, the area should be heavily mulched with
           straw or other suitable material.












































                                                                             67





                    DESIGN WORKSHEET FOR "PERC-RITE"T" SPECIFICATIONS


            1.   HOUSE SIZE          BEDROOMS             SQ. FT.
            2.          GALLONS PER DAY (GPD)
            3.   SOIL CLASSIFICATION
            4.   SOIL LOADING RATE                       GALLONS/SQ. FT./DAY
            5.   TOTAL ABSORPTION AREA REQ. (Line 2 L. Line 4)              SQ. FT.
            6.   DRIPPER LATERAL SPACING                       (STANDARD IS 2 FT.
            7.   TOTAL DRIPPER LINE REQUIRED (Line 5 = Line 6)
            8.   DRIPPER LINE LATERAL LENGTH (LONGEST):
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
            9.   SEPTIC TANK/ATU SI2E                   GALLONS
           10. DOSING TANK SIZE            GALLONS           GAL/INCH IN DEPTH
           11. DEPTH OF LINE
           12. ABSORPTION FIELD   LAYOUT: (CHECK ONE)
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
           13. ABSORPTION FIELD   ZONE SIZE:
               ZONE ONE               SQ. FT.              LINEAR  FEET
               ZONE TWO               SQ. FT.              LINEAR  FEET
               ZONE THREE             SQ. FT.              LINEAR  FEET
               ZONE FOUR              SQ. FT..             LINEAR  FEET
           14. FLOW RATES:       *USE THE LARGEST ZONE FOR THE     DESIGN*
               a. DOSING FLOW RATE (GPM)
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
               b. NUMBER OF RETURN    FIELD FLUSH CONNECTIONS
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
               c. FIELD FLUSH FLOW    RATE (Line 14b X 1.6 GPM)*
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
               d. TOTAL FLOW REQ. (Line    14a + Line 14c)*
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
           15. a. SUCTION LINE SIZE            INCHES AND LENGTH
               PRESSURE LOSSES (PSI)              SUCTION LINE LIFT
               b. FORC-E MAIN SUPPLY LINE   PIPE  SIZE IN INCHES
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
                   FORCE MAIN SUPPLY   LINE PIPE  LENGTH IN FEET
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
               PRESSURE LOSSES (PSI)
               c. RETURN FLUSH LINE PIPE    SIZE  IN INCHES
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
                   RETURN FLUSH LINE   PIPE LENGTH IN FEET
                      ZONE ONE         ZONE TWO        ZONE THREE         ZONE FOUR
               PRESSURE LOSSES (PSI)
           16. MODEL 20 PUMP AND FILTER    LOSS (PSI)
           17. ELEVATION RISE           PSI
           18. DRIPPER LINE LATERAL LOSS          PSI
           19. TOTAL PRESSURE REQ.: (TOTAL OF 15a-c+16+17+18 LOSSES)            PSI
           20. PUMP CAPACITY             GPM AT            PSI AT            LIFT
           21. PUMP MODEL #                      HORSEPOWER
           22. TIME DOSING PER ZONE
               ONE           GPM        MIN/DOSE         CYCLES        GAL/DOSE
               TWO           GPM        MIN/DOSE         CYCLES        GAL/DOSE
               THREE         GPM        MIN/DOSE         CYCLES        GAL/DOSE
               FOUR          GPM        MIN/DOSE         CYCLES        GAL/DOSE
           23. FLOAT  SWITCH DRAW DOWN                INCHES              GALLONS
           24. ELECTRICAL REQUIREMENT                VOLT                 A P
           25. CHECK VALVES ON SEPARATE RETURN    FLUSH LINEï¿½          YES        NO
           26* LANDSCAPE MODIFICATIONS NEEDED               YES           NO
           EXPLAIN:
           LOW FLOW WATER SAVING DEVICES USED               YES           NO


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           PART SIX

           Modified "Perc-Rite"" Systems Using Fill






                Most sites with a restrictive horizon or a seasonally high,
           water table within 24 inches of the surface are not suitable for a
           standard "Perc-Rite" TM System. Many are not suitable for any soil-
           absorption, waste-treatment system. But some of these sites can be
           used for waste treatment if the soil is supplemented with fill that
           has been carefully selected and added.

                When there is approximately 24 inches of usable soil on an
           acceptable site, a modified "Perc-Rite 11 TM System using some fill may
           be designed4      The existing soil must be of suitable or
           provisionally suitable' texture, structure and permeability. After
           the addition of some fill in order to maintain 12 to 18 inches of
           cover over the dripper lines trenches may be placed as shallow as
           3 inches into the natural soil. When there is less than 24 inches
           of usable soil a mound tv   system may be designed. The design and
           construction of mound systems will already have design criteria set
           by the local health departments which are used in other
           conventional soil absorption systems. The same criteria should be
           used when building a mound system for installation of a "Perc-
           Rite T" Drip Soil Absorption Systems.   Usually the fill material
           will be a soil with at least 25% course or medium sand and 50% fine
           or very fine sand (a Sandy Loam or Sandy Clay Loam type soil).
           Your soil scientist and local health department should be contacted
           regarding mound systems. Loading rates should always be determined
           on the most restrictive horizons under your fill or mound.


           Design of Fill or Mound Systems

                Other than the criteria described above, the only difference
           between designing a modified and standard "Perc-Rite  11 TM System is
           the calculation of the fill requirements. The volume of the fill
           necessary is the area to be filled multiplied by the depth of fill.
           The area to be f illed is the absorption f ield plus a f ive f oot
           buffer around the edges.

                Step 1. Calculate the area to be filled. Add 10 feet to the
           length and width of absorption area to allow for the buffer space.

                Example:   For a 60 feet x 30 feet absorption f ield to be


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          filled 1 foot deep:

               Total area = 70 feet x 40 feet

               Step 2. Calculate the volume of fill needed.

               Example:

               ï¿½ fill =  total area x depth of fill

               ï¿½ fill =  70 feet x 40 feet x 1 foot    2  800 ft3

               Step      Convert to cubic yards.

               Example:
               V fill        2,800 ft3
                         ---------------      104 yd3
                          27 ft3 per yd3

               The remaining design steps follow the procedure as described
          previously.


          Installation

               The success of a modified "Perc-Rite"" System depends on the
          care used in selecting and incorporating the fill material. The
          fill must have a Sandy Loam or Loamy Sand texture. The fill should
          not be hauled or worked wet.

               As with all "'Perc-Rite"Tm Systems, the site must be protected
          from traffic.   Prior to incorporating the fill, brush and small
          trees should be removed and the soil surface loosened using a
          cultivator or garden plow. It is very important that the soil be
          worked only when, dry.      Working damp or wet soil can cause
          compaction and sealing, leading to failure of the system.

               Fill is moved to the system using a front end loader, being
          careful to avoid driving on the plowed area.     The first load of
          fill is pushed Into place using a very small crawler tractor with
          a blade or a roto-tiller with a blade.     The fill is then tilled
          into the first few inches of natural soil to create a gradual
          boundary between the two. Failure to do this could ruin the system
          by forming a barrier to water movement at the soi '1-fill interface.
          Subsequent loads of fill are placed on the system and tilled, until
          the desired height is reached. The site should be shaped to shed
          water and be free of low spots before proceeding.





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