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How to Tell if Your Septic System Is Full

Updated March 23, 2017

Septic systems are designed to work for several years without maintenance. Wastes flow into a tank, break down naturally and are eventually released into a drainage area. But over time, sludge will build up on the bottom of the septic tank. If the sludge gets too high, it may clog the pipes or fill the tank to the point where untreated sewage is released into your yard or drainage area. Septic tanks must be pumped periodically to keep the sludge level down.

Examine the area above the septic tank for sewage odours, wet areas or patches of grass that are greener than the rest of the yard. A good time to check for these signs is just after doing laundry, when a lot of water has flowed into the tank. Any of these signs indicate that the tank is full, causing sewage to leak out.

Check to see if your toilets are flushing more slowly than usual. This could simply mean your pipes are partially clogged, but it also can result from a full septic tank.

Check for sewage odours in the house, particularly near drains. A properly functioning septic system should not release any odours.

Check for unusual wetness or standing water in the drainage area. A full septic tank will release sludge into the field, clogging the surface of the soil. This will prevent the soil from properly absorbing the water.

Measure the sludge depth with a stick. Wrap a white towel around the bottom of the stick and secure the towel to the stick with wire. Open the large inspection port at the top of your septic tank, and lower the stick to the bottom of the tank. Wait a couple of minutes, then slowly pull up the stick. Measure the sludge depth based on black particles stuck to the towel. If the sludge level is within 3 or 4 inches of the submerged outlet pipe, the tank needs cleaning.

Use the stick to measure the thickness of the floating scum layer. If the bottom of the floating layer is not several inches above the submerged outlet pipe, the tank needs to be cleaned.

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About the Author

Alan Sembera began writing for local newspapers in Texas and Louisiana. His professional career includes stints as a computer tech, information editor and income tax preparer. Sembera now writes full time about business and technology. He holds a Bachelor of Arts in journalism from Texas A&M University.