New York State Septic System Design Regulations 75-A.7 Distribution lines, distribution boxes, gravity flow, pressure distribution, dosing, siphons design specifications for septic systems InspectAPedia® -
Design specifications for piping between the septic tank and the drainfield or absorption bed
Design specifications for septic system distribution boxes
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Section 7 of the septic design regulations discusses the means of distribution or movement of effluent
from the septic tank to the absorption system or leach field. Components reviewed include septic tank outlet lines, effluent distribution lines, distribution boxes, gravity flow, pressure distribution, dosing, and siphons.
This document uses the New York State wastewater treatment standard for individual household septic systems
(Appendix 75-A) to provide an example of state regulated design and installation of both conventional
tank and leach field septic systems and alternative septic system
designs, including raised septic systems, septic mound systems, intermittent sand filter septic systems,
and evaportion-transpiration septic systems.
Also see SEPTIC CODES & REFERENCES and SEPTIC CONSULTANTS. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved
to the author. Technical review by industry experts has been performed and is ongoing - reviewers welcomed and are listed at "References."
Effective Date: 12/01/90
Title: Appendix 75-A.7 - Distribution devices
Section 75-A.7 Distribution devices [for Septic System Effluent. ]
(a) Gravity Distribution.
The maximum length of absorption lines used in conjunction with the
gravity distribution shall be 60 feet.
(1) Distribution Box.
(i) For accessibility, it is necessary that the distribution box be
located and have a removable cover not more than 12 inches below grade.
Where, due to site conditions, a distribution box must be greater than
12 inches below the surface, an extension collar shall be installed to
within 12 inches of the surface.
(ii) All outlets from the distribution box shall be at the same level to
insure the even distribution of flow.
(iii) To minimize frost action and reduce the possibility of movement
once installed, distribution boxes must be set on a bed of sand or pea
gravel at least 12 inches thick.
(iv) The drop between inlet and outlet inverts shall be at least two
inches. A baffle is required at the inlet side of the box when the
slope from the septic tank to the box exceeds 1/2 inch per foot or when
siphon dosing is used.
(v) There shall be a minimum two inch clearance between the inverts of
the outlets and the bottom of the box to prevent short-circuiting and
reduce solids carry-over.
(vi) Distribution boxes may be constructed in place or purchased
prefabricated. When concrete is used to construct boxes, it shall have
a minimum compressive strength of 2,500 psi at 28 day set.
(vii) Prefabricated boxes may be constructed of concrete, fiberglass, or
plastic. The boxes shall be installed in conformance with the
manufacturer's instructions in addition to the requirements above.
Readers of this page section on distribution boxes should also see
The D-Box a chapter of Inspecting, Testing, & Maintaining & Designing
Residential Septic Systems, our online book.
(2) Serial Distribution [of Septic System Effluent]
(i) In serial distribution, an upper distribution line is allowed to
fill before the effluent overflows into a lower line. This method is
acceptable for use with dosing systems only.
(ii) The connections between distribution lines is made with
non-perforated pipe placed in undisturbed soil.
(3) Drop Manholes.
(i) Drop manholes are used on sloping sites to reduce the velocity of
flow to lower distribution lines. This system may be used with gravity
distribution.
(ii) Baffles at the inlet end of the manhole and approximately four
inches from the inlet are required in drop manholes.
(iii) The inverts of all outlets in each manhole shall be at the same
level.
(b) Pressure distribution and dosing.
(1) These methods permit the rapid distribution of effluent throughout
the absorption system followed by a rest period during which no effluent
enters the system. The maximum length of absorption lines used in
conjunction with these methods shall be 100 feet.
(i) Pressure distribution utilizes a sewage effluent pump to move the
effluent through the pipe network and into the soil. The volume
discharged in each cycle will exceed the volume available in the pipe
network and will be discharged from the pipe under pressure.
(ii) Dosing involves the use of a pump or siphon to move the effluent
into the pipe network. Discharge from the pipe is by gravity. The
volume of effluent in each dose should be 75% to 85% of the volume
available in the pipe network.
(2) Dosing or pressure distribution is recommended for all systems as it
promotes better treatment of wastewater and system longevity.
(3) In absorption fields, single dosing units are required when the
total trench length exceeds 500 feet. Alternate dosing units are
required when the length exceeds 1,000 feet.
(4) The use of manually operated siphons or pumps is not acceptable.
(5) Pipe used in pressure distribution shall have a minimum diameter of
1.5 inches and a maximum diameter of three inches. Pipe for siphon
dosing is sized to conform with the volume of the dose and can range
from three to six inches in diameter based upon the volume of each dose.
The ends of all pipes shall be capped.
(6) Only pumps designated by the manufacturer for use as sewage effluent
pumps shall be used.
(7) Pump chambers shall be equipped with an alarm to indicate
malfunction. Siphon dosing systems normally include an overflow to the
distribution laterals. Pressure distribution systems shall not be
equipped with an overflow.
(8) Pump chambers shall be sized to provide a minimum of one day's
design flow storage above the alarm level. Siphon chambers shall have a
minimum total storage of one day's design flow below the overflow pipe.
Readers of this page should also see Pressure Dosing Septic Systems a chapter of Inspecting, Testing, & Maintaining & Designing Residential Septic Systems, our online book.
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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.
AEROBIC SEPTIC SYSTEMS
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 Manua [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. (DF volunteers to serve as indexer if Burks/Minnis re-publish this very useful volume.)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. We refer to it often.
While Minnis says the best place to buy this book is at Amazon (our link at left), you can also see this book at Minnis' website at http://web page .pace.edu/MMinnisbook
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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