Seepage Pits for Septic Effluent Disposal InspectAPedia® -
What is a seepage pit, and how is it different from a cesspool or drywell ?
What care is needed for a septic seepage pit?
What is the failure criteria for a septic seepage pit?
Questions & answers about designing, installing, using & mainteaining seepage pits for sewage or septic effluent disposal
This document explains what a drywell (or seepage pit) is, gives safety and maintenance advice for drywells, and defines the
criteria for drywell failure. We also explain the difference between a drywell and a seepage pit.
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What are Septic Drywells, What Drywell Maintenance is Needed? How do Drywells Fail?
We warn readers that while installation of a drywell to receive graywater at a property may be a good idea, the use of drywells for this purpose may be a warning about the capacity and remaining life of the septic system. This article series explains septic system and drywell or seepage pit or cesspool inspection procedures,
defects in onsite waste disposal systems, septic tank problems, septic drainfield problems, checklists of system components and things to ask. Drywell & seepage pit maintenance and
pumping schedules.
Readers trying to diagnose and deal with sudden soil subsidence or yard collapses should see CESSPOOL SAFETY WARNINGS as those hazards can also apply to drywells and septic tanks, and also see SINKHOLES, WARNING SIGNS. Additional septic system safety warnings are at SEPTIC & CESSPOOL SAFETY.
Drywells Used as Seepage Pits to Receive and Dispose of Septic Effluent from a Septic Tank
Seepage pits: a "seepage pit" may be used as a septic effluent absorption system such as shown in the sketch at the top of the page and also
immediately above.
In this application, instead of receiving only graywater, the pit is receiving not just graywater but also
blackwater-effluent or septic effluent which flows out of a septic tank. Unlike the drywell described just above, in this design
waste, including black water and gray water, leaves the building through a main drain which enters a septic tank. The tank
retains solids and grease/floating scum, allowing clarified effluent to enter the seepage pit for disposal into the soil.
Seepage pits come in a variety of capacities, sizes, shapes, and can be safe (against collapse) when a modern factory-built unit
is shown, such as those in this photo.
I do not consider the use of traditional seepage pits a complete and satisfactory onsite waste disposal system design,
though where space is limited or for other problem site
reasons it may have been the choice of the septic system installer.
Disposal of septic effluent deep below ground in a seepage pit (typically
four to six feet deep and placed another two or more feet below grade level) means that little or no aerobic bacteria will be present.
Limiting
the bacterial action to anaerobic may mean that the biomat that forms around the seepage pit will not adequately treat the effluent. The system
may then be discharging contaminants into groundwater and the environment.
Fortunately there are alternative onsite wastewater disposal alternative designs which can handle limited or even zero-space sites,
so a simple seepage pit as a destination for blackwater effluent is no longer the only choice for limited-space sites.
More Reading about Seepage Pits for Septic Effluent Disposal
(h) Seepage Pits used for septic system effluent disposal in "New York State Septic System Design Regulations 75-A.8 Subsurface treatment - disposal of septic effluent - design specifications for septic systems"
includes design specifications for seepage pits used to receive septic effluent, including tables of dimensions required
for different household loads.
Drywell and Seepage Pit Safety and Septic System Capacity Warnings
Drywell & Seepage Pit Safety
Safety Warning: do not walk over the top of or close to the edges of a drywell or any other onsite pit or excavation because
of the danger of fatal collapse. Keep pets and children away from such systems.
Safety Warning: there is a risk of drywell collapse, risking injury and potential fatality if someone falls in to one of these
systems, particularly for older site-built systems that were often made of dry-stacked stone or concrete block,
and more-so if such systems are not protected by a very secure cover. Believe it or not, simple wood board covers
were often used on home-made drywells. Such covers rot and ultimately collapse.
Drywell & Seepage Pit Capacity and Testing Limitations
Limited septic system capacity is implied by the presence of a drywell. Wet soil conditions or limited space
for a functioning drain field (for the septic system) often leads property owners to reduce the liquid load on
the septic system by routing gray water to a separate drywell. Where such a system is installed owners/buyers should
be alert for these conditions and should expect to face extra costs for system maintenance and repair as well as
limited septic system capacity.
An exception to the septic system capacity warning above at a large building where a sink or laundry are added in an area distant from piping
connected to the septic system, an owner may add a remote drywell as an alternative to inconvenient and costly routing
of a drain line from the laundry to the existing septic system.
Drywells can obscure or prevent effective septic loading and dye testing: If a drywell system is installed, running water at the fixtures draining into this system
(as may be done by some septic tests) are likely to fail to perform a loading test on the septic system even if such a test was attempted.
First, the fixtures where water was run in attempt to test the septic system (tank and leach field) may not even be delivering
water to those components if instead the fixtures drain to a separate drywell. It is critical to trace building drains as part of
a septic test or to otherwise try to determine if the test water is actually entering the septic system.
Even if we're trying to "test the drywell", if the drywell is "working" at all, it is a large empty hole in the ground. After a period of disuse it may appear
to be working during a test but fail in a day or two when the no-longer functioning hole is filled with wastewater.
Where a drywell is installed at a property and a septic inspection was attempted, more testing may be in order: in cases where only toilets empty into the septic system, it may be possible to make a more effective septic loading and dye test:
put a test water load directly into the toilet by using a garden hose.
This is not a typical/normal septic test procedure and has its own concerns
such as overloading a system of unknown design that did not anticipate such volumes and possible back-contamination of water supply via hose in toilet
(a cross connection). Whether or not such an additional test is performed, our warning about a system of limited capacity for which the owner
may face significant costs to repair or expand capacity remains in effect.
Tips for Extending Seepage Pit Life Life
Some experts recommend installing a filter on water entering the seepage pit. Particularly for a seepage pit
used to receive water not just from a septic tank receiving black water but also graywater from a clothes washing machine, installing a lint filter between the washing machine
and the seepage pit can extend the life of the drywell by reducing the moment of soil-clogging particles of
lint and debris into the system.
Intermittent dosing systems such as are used for some alternative septic system designs, can also be adapted
to graywater systems. In simple terms, this means that multiple drywells are used, and graywater is routed
intermittently among them, giving the unused drywell time to recover. A simple valve system on the
graywater drain line can serve
to route greywater (graywater) to alternating drywells.
Cesspools for more in-depth information about those systems.
Questions & Answers regarding this article
Questions & answers about designing, installing, using & mainteaining seepage pits for sewage or septic effluent disposal
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf.
Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include
Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and
Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by
Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)
...
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389
(2006), Advanced Onsite Wastewater Systems Technologies.
Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going
for homeowners but is a text we recommend for professionals--DF.
Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
Design Manuals for Septic Systems
US EPA Onsite Wastewater Treatment Systems Manual [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
"International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
"Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental
Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
Manual of Septic Tank Practice, US Public Health Service's 1959.
Onsite Wastewater Disposal Books
Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference for both property owners and septic system designers.
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
Planting Over Septic System Component", Daniel Friedman (author/editor, InspectAPedia.com), The Innovator, Winter/Spring 2008, BCOSSA, British Columbia OnSite Sewage Association, 201-3542 Blansard St., Victoria BC V8X 1W3 Canada
Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
Test Pit Preparation for Onsite Sewage Evaluations, State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design. Readers should also see Soil Percolation Tests and for testing an existing septic system, also see Dye Tests
Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill. Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers: * Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association
Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
The NSFC Products List has an excellent list of design manuals/modules available from their website or by telephone 800-624-8301
Submissions welcome. send us a suggested document link or request an exchange of website links
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