How to Install Septic System Drainage Systems


A septic system is made up of two components -- the septic tank, which traps the solid waste, and a drain field or leach field which disperses the liquids into the soil. Cities, counties and states in the U.S. all have their own laws regarding septic systems. Most states require a septic specialist or engineer to evaluate the soil for its filtering capabilities and to check that the proposed location of a new septic system is in compliance with setback laws and prescribed distances from nearby water sources. Some states allow noncertified personnel to install septic systems.

Things You'll Need

  • Mechanical digger or shovel
  • 3/4-2-inch gravel
  • Perforated PVC pipes
  • Distribution box
  • Contact your local health department to find out how to obtain a permit to install a new septic system or replace a failed drain field. When a new septic system is installed a reserve area is usually designated to be used for a replacement drain field if the original one fails. Most permitting authorities have records of all the existing septic systems in their region together with drawings showing the location and extent plus the reserve location.

  • Perform a soil test. A specialist can take soil samples to be examined in a laboratory and he may also pour water into holes to determine percolation speed. Sandy soil may percolate too fast and clay soil may not percolate fast enough for a "standard" drain field to be allowed. He will also measure the distance from your well, your neighbors' wells and watercourses including lakes, ponds, streams and even naturally occurring drainage depressions that carry water only when it rains and determine the depth of the groundwater under your proposed site. If your property does not qualify for a standard septic system you will have to pay an engineer to install an "alternative" system that does not have a regular drain field.

  • Dig two to five shallow trenches 18 to 36 inches wide and 1 to 2 feet deep in the area designated for the drain field according to the septic engineer's specifications. Slow filtering soil will require a larger drain field and more trenches. Line the bottom of the trenches with a bed of 3/4-2-inch gravel. Place perforated PVC pipes on top of the gravel bed. Join them with pipe sealing compound and use a distribution box to join them to the outlet of the septic tank. Cover with 6 to 12 inches of topsoil. In some instances you may have to place the pipes in specially designed filtration tubes or vaults to enhance the filtration process.

Tips & Warnings

  • Clear vegetation and large trees away from your drain field. Roots can clog the drain pipes and cause the system to fail.
  • Plant grass over your drain field to keep the soil together.
  • Do not build anything over your septic drain field or your septic reserve area.
  • Do not pave over your drain field.
  • Do not drive over your drain field. The soil needs to breathe and driving over it would compact it.
  • Do not allow large animals to graze on the drainfield.
  • Do not dig on the drainfield.

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