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Planting a Garden Over or Near Septic System Components - an illustrated guide
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
This article explains the types of gardens or other plants that should or should not be planted over or near septic fields or other septic system components.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Planting Fruit, Vegetable, or Ornamental Gardens Near or Over Septic Systems
This is a guide for homeowners who are planting trees, shrubs, gardens, ground cover, or other plants near a septic system and who need to know that can be planted near or over
septic system components like the septic tank, distribution box, and drain field or soil absorption system. Planting the wrong things or in the wrong places can lead to
the need for expensive septic system repairs.
Planting trees, shrubs, and even some ground covers over septic system components are causes of septic system failure in the drain field, leach field, seepage bed, or similar components.
Planting fruit trees, or vegetables (or anything else edible) over the septic drainfield might produce food that is unsafe to eat: see SEWAGE CONTAMINANTS in FRUIT / VEGETABLES for details.
Also see SEWAGE PATHOGENS in SEPTIC SLUDGE and SEWAGE NITROGEN CONTAMINANTS.
Question: Is it Safe to Eat Food Grown Near the Septic System?
I am trying to determine if it is safe to eat the lemons and tangelos [planted or grown] near the septic system of our home.- K.P.
The short answer is it's better to keep fruits and vegetables away from septic systems, especially
septic drainfields but above-ground crops such as fruit trees are less likely to be contaminated.
Watch out: gardening or planting anything but basic grass type groundcover over septic drainfields risks damage to the septic system by soil compression, damage to pipes, root invasion of pipes - all problems that can lead to costly septic system repairs.
Details and report of a study documenting bacterial hazards in fruits and vegetables actually watered with septic effluent [a more stringent test case] are at SEWAGE CONTAMINANTS in FRUIT / VEGETABLES.
Planting a fruit or vegetable garden over or near septic system components raises some important questions:
- Will there be pathogenic or chemical contamination of the soil (bacteria, viruses, cleaners) below the garden?
- Will septic system pathogens enter in or contaminate fruits or vegetables planted over or near the septic system?
- Will chemicals or salts passing through the septic system harm nearby plants?
- Will the garden planting itself harm the septic system in some way?
The effectiveness with which the soil biomat is treating pathogens in septic effluent, the ability of the soil to filter effluent,
the chemicals or salts entering the septic system, and the type of plants placed over or near the system are some of the
factors that lead to answers to these questions. [The photograph above shows our vegetable garden gone wild in Costa Rica.]
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- Septic effluent contains chemicals and pathogens which are potentially unhealthy or harmful to people, animals, or plants.
If a septic absorption system's biomat is functioning successfully, the level of these pathogens is reduced by up to 45% for conventional septic systems, up to 70% for advanced treatment systems, and for more advanced (and rarely found) systems it is possible to treat effluent to a level of sanitation similar to that of typical
surrounding surface water before effluent leaves the drainfield.
So there is a reasonable chance that food-plants located over or close to a septic drainfield contain harmful levels of bacteria or other contaminants. See SEWAGE CONTAMINANTS in FRUIT / VEGETABLES. The "safe" distances between edible crops and septic components depend on
- The level of treatment of septic effluent achieved by the onsite septic or wastewater treatment system
- The soil type (see below)
- The crop type (see below)
- Possibly seasonal or other changes in surrounding surface runoff and groundwater, independent of the individual septic system but affecting its performance and thus its level of treatment of the sewage
- Soil types affect how the septic system behaves and how it affects nearby plants of any kind.
Clay soils release cleared effluent in perhaps a few inches but then clay doesn't perc well and is bad in general for a septic location.
Sandy soils permit much greater travel of effluent and pathogens, certainly several feet.
These "close" distances do not even consider
what happens when the drainfield is not working well or is in failure. In that case pathogens may be released to the general
environment and might travel any distance from the septic field.
- Root crops such as carrots or potatoes which develop in the soil are likely to pick up pathogens from effluent in the soil
over, next to, or downhill from drainfield trenches or galleys.
- Leafy crops such as lettuce or perhaps broccoli which develop above the ground but close to it may be contaminated by pathogens that splash up
from the soil surface during watering or during rainfall.
- Above ground crops that grow on a raised vine such as cucumbers, tomatoes, or peppers may fare better if they must
be planted over or close to septic system components, since they are higher
up and less likely to be contaminated by soil splash-up.
- Salts and the septic system: Homes whose water supply is "hard" and which employ a salt-based water softener system are more likely to be passing high
levels of salt into the septic drainfield. Not only does this salt risk harming the drainfield operation (mineral clogging or
damage to the biomat) but such salts may also damage some plants that grow nearby.
- Chemicals and the septic system: At this website we've advised strongly against
use of "magic bullet" chemical or other septic treatments as some of them are toxic and environmental contaminants. Some of
these may also contaminate your garden. - see Using Root Killers.
- Gardening activities such as walking or digging into the first few inches of soil over a drainfield are not likely to
damage it.
But driving equipment such as a plow or roto tiller over a drainfield or constructing a "raised bed" garden which
requires the addition of soil above surrounding ground levels can damage the system or can reduce soil transpiration thus
preventing the drainfield from functioning properly.
Not "functioning properly" here means that the drainfield stops successfully
treating the pathogens that flow into it. It stops working and begins discharging unsanitary effluent into the environment, and
into your garden.
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- "Planting Over Septic System Components", 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
- "Planting on Your Septic Drain Field", Susan D. Day, Extension Associate; Ellen Silva, former Extension Technician; Horticulture, Virginia Tech. publication Number 426-617, Posted December 2000, published by the Virginia Cooperative Extension
- Escherichia coli O157:H7- US CDC
- Demistifying Ecoli - Federation of Ontario Cottagers
- Microbiology home page - US EPA
- Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
- Septic Contaminants, identifying - what are the Nitrogen contaminants produced by septic systems and what can be done about them if they escape initial treatment?
- Septic Tank Pathogens in Sludge and Floating Scum: what makes up the contents of residential sewage
- Measuring Septic Sludge & Scum Levels in Septic Tanks - Measuring the Level of Accumulated Solids, Sludge and Floating Scum in Treatment Tanks
- Sewage and Septic Contamination in Residential buildings - inspecting and testing for bacterial contamination after a sewage spill: consumer information and expert resources
- Septic Flood Response when and what to do to a septic system after area flooding
- "Remediation of Sewage Contaminated Crawlspaces", Byjim Holland, CR, "Cleaning and Restoration," July 1999, pp 22-24, original source: restcon.com/links/articles/Remediating%20Contaminated%20Crawlspaces.pdf
- Escherichia coli O157:H7- US CDC
- Cost effective testing for blackwater contamination in buildings Aerotech Labs
- Indicator organisms, testing for sewage contamination in buildings Aerotech Labs
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Inspecting Septic Systems: Online Book, Inspection, Test, Diagnosis, Repair, & Maintenance: our Online Septic Book: Septic Testing, Loading & Dye Tests, Septic Tank Pumping, Clearances, details of onsite waste disposal system inspection, testing, repair procedures.
- 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.
- 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
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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
- 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
- Save the Septic System - Do Not Flush These Items Down the Toilet, Daniel Friedman, InspectAPedia.com - PDF document, printable
- SEPTIC STANDARDS
- SEPTIC MAGAZINES
- 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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