Gravelless Septic Systems - Geotextile-Wrapped Designs
Gravelless or "no-rock" septic system designs:
This article explains design of gravelless or "no gravel" or "no rock" septic
drainfield systems using geotextiles and offering installation specifications. Drainfields, also called leach fields, absorption
beds, soil absorption systems, and leaching beds, perform the functions of septic effluent treatment and disposal
in onsite wastewater treatment systems, conventionally called "septic systems".
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Use of Geotextile-Wrapped Perforated Pipe for Onsite Wastewater Treatment and Disposal
Gravelless Systems - Gravelless Septic Absorption Systems
There are three typical gravel-less effluent disposal systems in current use and shown in the US EPA sketches below (originally from NSFC)
and I describe a fourth variation which is provided by some manufacturers:
This article describes the second type - Geotextile-wrapped designs.
Gravelless septic systems or "no gravel" septic system trenches use plastic or other prefabricated wastewater distribution systems which
are buried in soil without the use of surrounding gravel. Typical gravelless septic systems use a plastic chamber,
a geotextile-wrapped pipe, or a polystyrene-wrapped pipe to distribute effluent into the soil.
The necessary soil absorption area is provided
by the perforated surface of the gravelless septic system components (or by soil at the bottom of a chamber) themselves rather than by the gravel and
trench walls of a conventional septic drainfield. These systems can provide an acceptable effluent disposal system for sites with limited space for a drainfield
or where gravel is not available or is quite expensive.
2. Geotextile-wrapped perforated pipe buried in an earthen trench.
In this type of system, a large diameter corrugated plastic pipe
(eight inches or greater in diameter) surrounded by a hydrophilic
geotextile is installed in an excavated trench using only the original
soil as backfill.
Other systems utilizing products such as galleys,
flow diffusers or leaching chambers can be installed without aggregate
One linear foot of these products shall be equivalent to one
linear foot of conventional (24 inch wide) absorption trench.(1)
For an example of this geotextile-wrapped pipe approach to wastewater
disposal using 8" or 10" diameter piping, see Crumpler Plastic Pipe's "No-Rock TM Septic-Leachate drainpipe systems" listed at Product Sources below.
CPP informs us that
because the square foot equivalent leaching area when this system is used is not a foot-for-foot ratio based on a 36" trench, the
8" & 10" CPP Filter Wrapped systems are typically longer than the traditional septic drainfield trenches. Although the
individual line length may be longer, the CPP system may actually require less total square footage of lot space if
the on-center line spacing is controlled by the excavated trench width treatment
plume & not an "arbitrary CODE stipulation".
According to CPP, this added length achieves superior distribution to the trench sidewall where the
bulk of the septic liquid enters the soil for treatment. [One reason for wider trench on-center spacing advanced
by some health departments is to assure that the site affords space for future trench line replacement .--DF].
Most sanitary or health department codes size 8" diameter Geotextile-Wrapped Perforated Pipe to equal a 2 Foot wide
conventional septic drainfield trench, and similarly size 10" diameter Geotextile-Wrapped Perforated Pipe to be
equal to a 2.5 foot wide conventional drainfield trench.
In determining how much leach field area shall be provided
when using Geotextile-Wrapped Perforated Pipe, most state codes (where they have them) will require that the cubic footage
that would have been required if a conventional 3-foot wide conventional perforated pipe & gravel leach field system had been
installed will be used to determine the size 2 Foot or 2.5 Foot wide gravelless systems as well.
Thus if 100 feet of a conventional gravel system in 3 Foot wide trenches is required for one bedroom (or 300 Cubic Ft), then
150 feet of 8" Geotextile-Wrapped Perforated Pipe will be required or 120 feet of 10" diameter Geotextile-Wrapped Perforated Pipe.
Sketch of geotextile-wrapped pipe in plan view, courtesy of Crumpler Plastic Pipe - CPP - links below.
For OC (On-Center) spacing of parallel lines treating sewage from a 2 bedroom home, a conventional gravel system of 100 foot length
would require 1200 square feet of lot surface area if 3 times the actual 'excavated' trench width is used for OC separation.
In comparison, for an 8" Geotextile-Wrapped Perforated Pipe system,
which can be placed in a 1.5 Ft(18") wide trench, 1,125 square feet of lot surface area would be required.
For a 10" diameter
Geotextile-Wrapped Perforated Pipe, which can be placed in
a 1.5 Ft (18") wide trench, 900 square feet of lot space is needed.
If a different or as CPP puts it "arbitrary" OC trench width spacing is mandated
(ie: 5 ft or 7 Ft OC required regardless of 'excavated' trench width) by a state code, then the lot surface area calculations
will of course be different. [Thanks again to Crumpler Plastic Pipe, Inc. for this added detail. Links to this company's website and products
are provided below.]
What all this means is that for a given building usage and set of soil conditions,
whether or not the Geotextile-Wrapped Perforated Pipe system is going to provide the necessary
effluent handling capacity in a smaller total square feet than a conventional drain field would require
depends on the on-center spacing requirements set by the local authorities.
Continue reading at GRAVELLESS SEPTIC CHAMBER SYSTEMS or select a topic from the More Reading links shown below.
Or see GRAVELLESS SEPTIC SYSTEMS - home
Suggested citation for this web page
NO-ROCK SEPTIC GEOTEXTILE-WRAPPED PIPE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
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Technical Reviewers & References
Publisher's Google+ Page by Daniel Friedman
Click to Show or Hide Citations & References
- New York State Department of Health, "Appendix 75-A Wastewater Treatment Standards - Individual Household Systems", [PDF] New York State Department of Health, 3 February 2010, retrieved 3/1/2010, original source: https://www.health.ny.gov/regulations/nycrr/title_10/part_75/appendix_75-a.htm
- Crumpler Plastic Pipe, Inc. Crumpler provides fabric-wrapped drainage piping 800-334-5071 Roseboro NC USA - "No-Rock TM Septic-Leachate drainpipe systems" are available in 8" and 10" systems.
- Jeff Pildis, Technical Service & Support, Infiltrator Systems, Inc. 800-718-2754
- How Big Should the Leach Field Be? includes a practical example using sample calculations and a table of soil percolation rate vs. field size
- (1) (2) (3) (4) APPENDIX 75-A to Public Health Law, 201(1)(1) NEW YORK STATE WASTEWATER TREATMENT
STANDARDS - INDIVIDUAL HOUSEHOLD SEPTIC SYSTEMS. Portions of
the text of this web page (using paragraphs identified by parenthetical numbers (1)-(4)) are quoted from this document,
expanded with edits and additions by this author
- "Gravelless Drainfields, Recommended Standards and Guidance for Performance, Application, Design and Operation & Maintenance",
Washington State Department of Health, an MS Word .doc file available at: www.doh.wa.gov/ehp/ts/WW/Gravelless2004.doc
- 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.
- How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
- Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
- Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.
- 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
- 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). 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 I 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.
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)
- Eco John® Innovative Toilet Solutions, Global Inventive Industries, Fountain Valley CA, PDF, product brochure
- "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
- Soil Percolation Tests soil perc testing guide and instructions
- Percolation Testing Manual, CNMI Division of Environmental Quality, PO Box 501304, Saipan, MP 96950
- 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
- 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