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What Is A Septic System Drain field?

By Rizwan Ahmad - 05 March 2013 1 Comment
The septic system drain field removes toxic materials from the contents that are drawn out of the septic tank. The drain field is made up of trenches that also contain gravel and a series of pipes, which then has dirt or soil placed on top of it in order to prevent animals from getting in and disrupting the wastewater.

This keeps the runoff that is found on the surface from getting into the wastewater, as well. Often the pipes in a drain field have a diameter that is four inches and the trenches are usually dug with a width of two feet and a depth of four to six feet. The gravel is placed in the drain field typically about two to three feet deep. Then soil is piled over this gravel. When effluent water enters the drain field, the gravel and soil gradually absorb it.

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The soil used in the drain field system has to pass certain tests in order to make it suitable for receiving wastewater. This means that a percolation test is often distributed. This test determines the soil’s absorption rate. It is conducted by measuring the length of time a quantity of water is absorbed by this soil after drilling a hole into the subsoil area of a drain field. The depth of these holes is pre-determined. One kind of percolation test that is used in a drain field is known as leach line testing. Leach line testing requires a minimum of three holes to be drilled, all at varying depths. Sometimes more holes are drilled, however, creating a pattern across the field.

These tests are performed on drain fields to ensure permeability rates for the soil allow for the septic liquid to be percolated away from the drain field area, but also to make sure that it has the right texture to act as a filter to get rid of the pathogens in the wastewater prior to their reaching a public supply of water.

Drain field size is determined by the absorption rates of the soil and gravel used. A smaller drain field indicates that the soil used to absorb the wastewater is very absorbent and can absorb the materials quickly. Larger drain fields are found in places where the soil that is used to absorb the wastewater is clay, which has a slow absorption rate. Similar rates of absorption are found in areas where silt is the main soil. Gravity is the main force working on septic systems, and this explains why drain fields are built lower than the septic tanks which are lower than the homes and buildings that use the septic tanks.

When there are septic system problems, sometimes the drain field is the culprit. Sometimes the drain field experiences an overload of water, often referred to as hydraulic overload, and other times there is an accumulation of organic material, which causes it to clog and fail. When a drain field fails, this has a detrimental effect on public health, because the untreated water can find its way into the public water supply.

Homer Jephson is an operations manager at Pinnacle Environmental Technologies, a company focused on providing affordable waste water treatment, in Langley, BC. He believes it is important to educate and make people aware of the process and precautionary measures they can take to ensure that they receive clean water in their taps.
Rizwan Ahmad
About the Author:
This article is contributed by Homer Jephson and posted by Rizwan Ahmad Author and founder of, He is a tech blogger from India and he loves to share his thoughts by writing articles on this site to the different topics related to technology world,


1 comment to '' What Is A Septic System Drain field? "

  1. Thanks a lot for the information that you have shared. This can serve as a great tool in cleaning the environment especially the water system.