PHOTO of melting snow and depressions indicating septic drain field trench locations. Just Where to Look to Find the Septic Drainfield

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How to use visual clues to find the seepage beds or leaching field:

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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Visual Clues that Indicate Drain Field Location

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.

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 walk through example of that procedure.

PHOTO of an apparent drain field location where fill has been added.

If you cannot find any candidate locations for a drainfield, go back to "square one" and start with our SEPTIC TANK, HOW TO FIND 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 SEPTIC DRAINFIELD SIZE 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.

PHOTO of a stepped-mound system with inappropriate plantings on its sides.

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.

Lawn shown is a candiate for locating septic tank and drainfield

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.

PHOTO of melting snow and depressions indicating septic drain field trench locations.

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:

  1. 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.
  2. 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

Image of a failed septic system and deep snow cover

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.

VISUAL CLUES LOCATE the DRAINFIELD contains additional clues that telltale where you can expect to find the septic drainfield.

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."


Continue reading at VISUAL CLUES LOCATE the SEPTIC TANK or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEPTIC TANK, HOW TO FIND for details about finding the septic tank or chamber or drywell or seepage pit.



Or see How to Find the Septic Tank. More videos on septic system location & maintenance are at SEPTIC VIDEOS

Or see these

Septic Drainfield Location Articles

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