Environmental Health
Septic Systems
Septic Systems
Operation and Maintenance
  Locate Your Drainfield  
  Record Drawing  l  Tips to Locate Your Drainfield  

You know your septic system drainfield is out there… but just where is it? It is important to locate it so you can avoid damaging it by:

  • Paving over the drainfield
  • Parking or driving heavy equipment over the drainfield
  • Planting trees or shrubs too close to the drainfield
  • Disturbing the soils with a landscaping project or livestock

It is also important to know where your drainfield is located, so you can check the drainfield for problem signs, such as soggy soil and odors.

Record Drawing

Diagram of septic systemGet a copy of the record drawing for your system. The septic system "record drawing" (previously referred to as an "as-built") is a diagram showing where your septic system components are located.

You can download the Request for Record Drawing/Permit Information [PDF] or contact the Thurston County Permit Assistance Center (PAC), 360-786-5490. The PAC is located at 2000 Lakeridge Dr. SW, Olympia, on the second floor of Building 1 (PAC Hours of Operation [PDF] - Limited Hours Please Check Before You Leave). When you call or visit, please have your eleven-digit tax parcel number ready. This is the number that appears on your county tax statements. (If you do not have your tax parcel number, contact the County Assessor's office.)

The quality and detail of record drawings vary greatly. An older diagram (prior to 1980) may be a very rough, simple sketch showing the layout of your system. A newer diagram will show the tank, drainfield, replacement area (for future use if a replacement field is needed), and any other components of your system, such as a pump chamber or mound. The size of the tank and length of the drainfield lines may also be noted.

Tips to Locate Your Drainfield

If a copy of your record drawing is not available, try the following tips to locate the drainfield.

  • In late summer, if you stop watering your lawn you may see green stripes in your yard. These are the damp areas along the drainfield pipes. In the winter, the areas above the pipes may be the first place frost melts in your yard.
  • Do you have monitoring ports or clean-outs? These are white-capped tubes or pipes, cut off at or near the ground surface. They allow you to check the liquid level in the drainfield pipes and are located at the ends of the pipes.
  • Carefully probe the areas leading away from the septic tank. Avoid using heavy steel wrecking bars or similar probing tools that can damage the septic tank top or other components.
  • Look for clues such as shallow, parallel depressions, which may mark the drainfield trenches. It is unlikely that a drainfield could have been installed among large trees or in very rocky areas.
  • Go under the house and look where the sewer pipe exits the foundation. The septic tank is usually within 10 feet of the foundation.
  • Hire a professional company to send echo-locators down.

For more information on troubleshooting problems,
contact the Septic Help Line at 360-867-2669.

Septic Helpline

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This page last updated: 01/28/22