Start your search for the septic tank lines -- the leach field -- at the house. Trace the plumbing drain lines to the septic tank usually installed 10 to 20 feet from the home's exterior. At the tank's end opposite the house, the drain line leads to the leach field. Check the natural slope of the land to locate the leach field. When searching for drain lines, never use heavy machinery, wrecking bars or jackhammers. Call your local electric utility provider or gas company to locate buried gas or utility lines before digging.

Inside of perforated tube
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Perforated pipes in the leach field drain the liquids into the ground.

Septic System Basics

A septic system consists of a tank to hold solids and the leach field that drains the liquids. A baffle or wall inside the tank separates the solids from the liquids. The liquids disperse into the ground by a drain line that connects to perforated pipes dug into trenches and laid on a bed of gravel, where the liquids are absorbed by the soil. Issues occur when pipes are blocked or drain fields become too saturated with liquid. Other problems include improper location, design flaws or poor installation

Regular Inspection

Professionals recommend that you inspect septic tanks, and if necessary, pump them out every three years. If you have issues with gurgling sounds in your home, or water backs up after the system is serviced, the cause could be a saturated drain field, but water logged or compromised drain fields cannot be repaired, a new drain field must be constructed for the septic to work again.

Check for Cleanouts

Look for capped cleanouts that sit vertically above the ground a few inches in the leach field itself or look behind a wall or in a closet in the basement. The cleanouts allow you to check the liquid level in the drain-field line when it is open. If you have no other information, visually trace the orientation of the pipe from the cleanout. Some drain fields have cleanouts at the beginning and end of the leach field.

Natural Indicators

A wet or swampy area that never dries could indicate the drain field. Grass or vegetation that greens in stripes when grass around it browns offers a solid clue as to its location. Lack of snow or frost in a specific area during the winter may be another telltale sign. If you run hot water into your system, it can cause snow or frost to melt above the drain lines. Look for shallow depressions running parallel to each other that mark drain field trenches. If you have a deep system -- a basement requires a deep system -- natural indicators do not typically apply because the drain field is too deep. But if you smell a foul odor, the system is likely in need of maintenance, regardless of how deep it is.

System Drawings

The blueprint or drawings for septic system installations are on file with the local health department, as long as the system was built with a permit. The location, layout, components and any other details of the drain field are usually found on the drawings. If your search doesn't turn up any relevant results, request a record search on your street address or the tax account number for the property. Fill out a "Request for Copy of Septic System Drawing" form, and submit it to your local health department. The agency -- if they have the record -- will mail it to you. If that fails, contact the previous owner of the home.

Professional Help

Enlist the help of a disposal system contractor or a licensed liquid waste hauler to locate the septic system if you don't have a drawing. The search typically focuses on the septic tank first and then the layout of the drain field lines. You can also pick up a flushable transmitter from a plumbing or rental store or a tank cleaning company. Once the transmitter flushes down the toilet, a hand-held receiver picks up its signal.

Distribution Box

Some septic tanks have an additional distribution box a few feet from the tank, on its downstream side. The box channels water into the trenches via ports and pipes. If your system has a distribution box, it should have a lid that reveals the direction of the ports that lead to the drain field lines. It's possible to locate the box with a probe, but be careful. Don't use excessive force with the probe that may cause damage to the box.

Size and Scope

The size and scope of your drain field depends on your home and the type of soil you have. The drain line exits the tank parallel to the intake, but individual drain lines may run perpendicular to the intake line, fork into an H-pattern or other patterns that fit the land. The lines should not be closer than 10-feet apart and no longer than about 100-feet long.