Planting Ground Coverings Over Septic System Components - an illustrated guide
GROUND COVER, IVY OVER SEPTIC FIELDS - CONTENTS: Ground cover over septic fields - planting guide - Advice for planting grasses, flowers, pachysandra, ivy, or other ground covers over or near septic systems
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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.
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
FAQs below discusses field reports of problems & solutions for this topic
Frequently Asked Questions (FAQs) about which plants are suitable for planting over septic drainfields or evaporation-transpiration systems
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"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
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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.