Septic System Design Flow Rate Specifications
Sewage flow rates & model regulations for septic designers
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Sewage or wastewater flow rate assumptions & specifications for septic designers:
These model septic design regulations discuss sewage flow rates to be used in designing onsite wastewater
treatment facilities for individual households.
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.
Photo above: the wesite author (third from left) at Camp Virginia where the onsite waste disposal system consisted of a latrine fondly named Oklahoma. To go to the toilet we'd say "I'm going to Oklahoma".
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Sewage Design Flow Rates & Regulations
Model source: New York State Septic Regulation Appendix 75-A.3 - Sewage flows - Effective Date: 12/01/90 or later and cited in detail at REFERENCES. The page top photo of campers at Camp Virginia (1950's) appears in our detailed discussion of OUTHOUSES & LATRINES.
Definition of daily design flow of wastewater
The daily design flow is the volume of wastewater that should be assumed when determining the volume of wastewater that the sewage system (septic system or soakbed or drainfield or other treatment system) must be capable of handling. "Handling" means both adequate treatment and disposal without discharge of wastewater to the surface, to nearby waterways or to other unacceptable locations.
The following table gives septic system design flow rates that shall be assumed by septic system designers, giving flows in gallons of wastewater per day per bedroom in the home served by a private onsite wastewater disposal system, that is, a private septic system. Different septic design flow rates are assumed depending on the modernity and efficiency or water usage rate of the plumbing fixtures in the home. --DF
(a) Roof, footing, garage, cellar and surface water drainage must be
excluded from the system. Water softener, water recharge and backwash
wastes normally are not to be discharged to the system unless a separate
subsurface discharge to an area 250 feet from wells or water courses is
(b) Minimum design flows for various configurations of plumbing
fixtures shall be as shown in Table 1.
NYS Appendix A-75 Table 1: Septic System Design Flow Rate Data
Plumbing Fixture Age & Water Flow Rates
Septic System Design Flows
Gallons per Day (GPD) per Bedroom
Post-1994 Water-saving plumbing fixtures: water-saving or low flow-rate fixtuires designed / produced after 1994
1.6+ gallons per flush (GPF) toilet &
2.5+ gallons per minute (GPM) flow-rate faucets & shower heads
Pre-1994 Standard plumbing fixtures: conventional fixtures produced before 1994
3.5 gallons per flush (GPF) toilet &
3.0 gallons per minute (GPM) flow-rate faucets & shower heads
Pre-1980 Standard plumbing fixtures: conventional plumbing fixtures produced before 1980 that use the larger water volumes shown below
1GPF or less with new standard fixtures (3.0 GPM max)
Waterless toilet (e.g. composting toilet) with new standard fixtures (3.0 GPM max)
75 Greywater Only
Notes to the table:
This table is adapted from the New York State Department of Health regulations Appendix 75-A part 3 with additional text and comments to clarify the different categories of plumbing fixture water usage rates.
GPF = gallons per flush at the toilet. Note that for dual-flush toilets that use a smaller flush volume when only liquid waste is present may use still less water but the flow rate assumptions in the NYS table address the alternative, solid-waste larger flush volumes of these fixtures.
GPM = gallons per minute of water flow at the faucet or shower head
Actual Septic or wastewater drainfield size (leach field size, soakbed size, soakaway bed size, absorption trench size) is given as drainfield trench lengths and dimensions in Table 4A, Septic Wastewater Effluent Input Flow Rate (Gallons per Day) found at SEPTIC DRAINFIELD SIZE
Continue reading at SEPTIC DRAINFIELD SIZE where we provide wastewater application rates and a detailed table of septic soakbed or leachfield or drainfield size as a function of soil percolation rate and wastewater volume flow in gallons per day, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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, 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
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.
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.
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.
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