The Septic Tank Drain Field
The septic tank drain field (or leachfield) is the second
part of the septic system. The other main part being the tank.
What the drain field does:
When waste water goes out of your home, it ends up in the tank first. The heavy solids settle to
the bottom and the lighter ones float to the top forming a scum layer.
The waste water in the center of the tank that is now separated from the solids is pushed to the
drainfield when more waste water comes into the tank.
The location of the septic tank drain field:
It should not be built near a steam or lake. The waste water can seep from the soil and contaminate
those bodies of water.
It should be constructed in an area where drainage is good. But not in a low lying area where
flooding and ponding of water occurs such as after rains. The soil needs to be able to absorb the waste water. A
percolation test may be needed to see how well the soil absorbs water.
The drain field is constructed by digging trenches. This is usually done with a backhoe at the time
the hole is dug for the tank. The ditches have to be a certain width and depth to accommodate the pipes that are
laid in them later.
The pipes have small holes allowing the waste water to drain into the soil. Gravel is normally put
over the pipes and then soil to make it level with the surrounding ground surface. Grass can then be planted to
Do not plant trees or shrubs over the lines. The roots can destroy the drain field. Also don't
drive a vehicle or heavy equipment over the field.
Infiltrator System: This type of septic tank drainfield uses plastic chambers
instead of pipes and gravel. Its said to be more efficient at distributing wastewater into the soil.