Planting Ground Coverings Over Septic System Components - an illustrated guide
This septic system design and maintenance article discusses the types of plants that should or should not be planted over or near septic fields or other septic system components. 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.
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Planting Ground Cover Over Septic Fields
There are several problems that can be caused by planting the wrong thing on top of or too close to septic system drainfields or soakaway beds. Among these we are concerned with possible sewage pathogens that may enter and contaminate edible fruits or vegetables grown on or too close to septic fields, and we are concerned as well that the roots of plants too close to the septic system can invade and clog system piping, leading to costly septic field repairs.
But here we address a less well known but equally important problem: some plantings can interfere with moisture evaporation from the soil below - transpiration: the movement of septic effluent moisture from the soil into the air by evaporation. Transpiration is an important ingredient in wastewater disposal in many septic system designs.
What Ground Cover Should Not Be Planted over Septic Systems?
Ivy, Pachysandra, Similar Ground Covers are NOT OK for use over a septic drainfield: these
plants will reduce effluent evaporation from the drainfield, soil absorption system, soakaway system, or mound soils.
A second reason to keep these plants away from septic system fields is because
their roots often invade and clog effluent distribution piping.
The photographs above
show pachysandra as a dense ground cover (at left) and typical ground cover north of the arctic circle in Norway (at right). Thick dense vegetation of any sort
will conserve moisture to itself and will prevent soil transpiration.
Over a septic system this
means that the portion of effluent disposal that is supposed to be occurring due to evaporation will be reduced and
the liquid load on surrounding soils increased - you've cut the effectiveness and shortened the life of the drainfield by
These plants are OK, however, for planting over the septic tank itself.
What Ground Cover is Acceptable for Planting over Septic Systems?
Wildflowers and ordinary grasses are just fine for planting over a septic system and any of its components.
shallow-root plants that do not invade the system piping, they stabilize the soil surface, and they do not interfere with soil
transpiration, the movement of needed oxygen into the upper soil layers (needed by the soil biomat below the drainfield) and the
evaporation of a portion of septic effluent that enters the drainfield.
The photograph shows a field of wildflowers in
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.
Continue reading at TREES or SHRUBS OVER THE SEPTIC FIELD or TANK or select a topic from the More Reading links or topic ARTICLE INDEX shown below.
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Technical Reviewers & References
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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
- "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 coliO157:H7- US CDC
- Demystifying 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 SYSTEM FLOOD DAMAGE REPAIR when and what to do to a septic system after area flooding
- Remediation of Sewage Contaminated Crawlspaces - By jim Holland, CR, "Cleaning and Restoration," July 1999, pp 22-24
- Escherichia coliO157: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
- 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.