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Exactly where should you look to find the septic drainfield or soakaway bed? This article helps you find a septic tank, D-box, soakaway bed or drainfield and other components by identifying locations at a building site where those components could fit and should have been placed.
Where should we expect to find a septic system drainfield or leachfield when we're exploring an existing homesite?
This article series and our accompanying septic system location videos explains how to find the leach field or drainfield portion of a
septic system.
We include sketches and photos that help you learn what to look for, and we
describe several methods useful for finding buried drainfield components. (Septic drain fields are also called soil absorption systems or seepage beds.) Also see How to Find the Septic Tank.
The septic system video#3 at right describes walking an 18 year old homesite by a lake to find the septic system components. We observe one area that by its space and absence of trees and rocks is almost certainly the drainfield location - a fact later confirmed by the owner.
This particular drainfield is uphill from the septic tank and the home which it serves. A septic pumping system will be needed. More videos on septic system location & maintenance are at SEPTIC VIDEOS.More videos on septic system location & maintenance are at SEPTIC VIDEOS.
Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved
to the author. Technical reviewers and content suggestions are welcome and are credited at "References."
Suppose we have no documentation and no idea where the drainfield is located.
You can walk the building site looking for where a septic field could possibly be placed based on space, soil, and terrain conditions as well as distances from property boundaries and from a well if one is present. Our video at the top of this page gives a site walkthrough example of that procedure.
If you cannot find any candidate locations for a drainfield, go back to "square one" and start with our Septic Tank Location article. Once we can find the septic tank itself, the septic tank outlet defines the location
of the effluent drain line that leads to the leach field. But remember that a drainfield may not be installed at all. There could be a seepage pit, or nothing, yet the septic system may appear to be working, depending on the level of its usage and soil characteristics.
An experienced contractor or inspector can often tell where the leach field is by a simple visual check
of the property since s/he knows the typical size, elevation, and soil requirements - in other words, we look
to see where a leach field could possibly be fit at a property.
In the photo our client is pointing to a filled-area at the front of his home - which we determined
was the probable drainfield area. Unfortunately the installer put his fill right across a
creek bed (look in the upper photo at the natural lay of the land). So the drain field did not have
much of a life before its effluent leaked into groundwater, appearing in our test as pink-dyed
effluent in a nearby stream.
Our article Absorption Field Design discusses how to locate the septic field and how to determine septic field size for
a conventional drain field. Knowing these most basic design considerations can tell you where to look for septic fields at a building site by knowing where a working field might be expected to be installed.
If a property has an alternative design system such as a mound or raised bed or other
special absorption field designs, those will be more obvious as a terrain feature. You'll see
a rather large, rather flat area of raised soil or filled soil on the property.
Sizes can
vary widely but a small constructed drainfield made of fill might be
30' wide x 50' long. In the photo a two-level or "tiered" septic mound was installed
perhaps 20 years ago; the lower mound is visible in the foreground.
The shrubs are a bit close
to the septic field, which we found was in failure - dyed septic effluent appeared in the
driveway in the close foreground, and could be seen quickly in this drain basin intended we were told to remove water from the driveway. Actually it was removing
septic effluent from the drive.
There may be good visual clues that indicate the drainfield location, especially if you know
what to look for.
Areas Cleared of Rocks and Major Trees Often Marks the Location of an Older Drainfield
This older and mature lawn is free of large trees and rocks though those items are found at other areas of this building site. This is where we expected to find the septic tank and drainfield.
Often it is possible to see long parallel depressions which mark leach field trenches.
You cannot see them in this photo (a tank and seepage pit were found later) but you can see them in the next section of this article. These depressions are caused by earth fill settlement over the drainfield trenches.
They may
be visible in systems of almost any age. Long parallel depressions, perhaps 24 to 30" wide and
many feet long, perhaps 20' to 40' and spaced perhaps 4' to 6' apart are suggestive of
drain field trenches.
Areas of Snow Melt may Show Drainfield Layout, Trench Lines, Location
In northern climates when there is light snow cover, the drain field
depressions may be easier to see for a couple of reasons:
the snow cover forms a smooth
blanket which more easily shows-up depressions, especially in late afternoon light when the
sun is low in the sky and shadows are more obvious.
Because septic effluent is flowing into
an in-use drainfield the trench areas may be a bit warmer than the surrounding soil, causing
snow to melt or be thinner over the trenches, and adding to the "depression" effect.
Wet Areas may Show a (failing) Drainfield Location
It's too bad, but sometimes the leaching bed or drainfield location becomes obvious because it is in failure mode.
If a drainfield is failing by pushing effluent to the surface that is a rather obvious clue
of the field location.
The effluent breakout most-often occurs at the low-end of the failing
drainfield line(s), but it can occur anywhere that a pipe is clogged, damaged, or leaking. In this photo, which we discuss in more detail below, the septic system failure and thus the septic field location was visually evident even under deep snow cover.
Often it is possible to see an area of raised-fill which was built to house the leach field.
Questions & answers or comments about looking for the septic drainfield or soakaway bed or leach field
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Percolation Testing Manual, CNMI Division of Environmental Quality, Gualo Rai, Saipan provides an excellent English Language manual guide for soil percolation testing. Original source: www.deq.gov.mp/artdoc/Sec6art108ID255.pdf
Soil Test Pit Preparation, fact sheet, Oregon DEQ Department of Environmental Quality, original source www.deq.state.or.us/wq/pubs/factsheets/onsite/testpitprep.pdf The Oregon DEQ onsite water quality program can be contacted at 811 South Ave, Portland OR 97204, 800-452-4011 or see http://www.oregon.gov/DEQ/
Thanks to reader Michael Roth
for technical link editing 6/29/09.
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.
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., Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
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.
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.
The Home Reference Book - the Encyclopedia of Homes
