Considerations for Installing a Drainfield

Before a septic/drainfied design can be established, the first thing that must happen is for Soil Logs to be taken by the On Site designer. Once the design has been completed and approved by the county Health Department construction can begin. The most simple drainfield that can be employed is called a gravity flow system. No pumps are required.

Normally one length of drain pipe is employed for each bedroom authorized by the building permit. Therefore, for a three bedroom system, three lines would emanate from a main junction outside of the septic tank. The length of each line and the diameter of the pipe determine the volume of the effluents that can be dispersed as a function of time. Each line has a number of drain holes along the length of pipe which allow effluents to pass into the ground. The kinds of soils in the area where a drain field will be located have a significant bearing on the design. The more porous the base soil, the faster effluents disburse. The slope of the lines, the amount and size of the gravel or other base material placed within the trench beneath the lines are important considerations for proper functioning of a system.

Most effluents are disbursed and absorbed within the first few feet beneath their trenches. The water that remains continues to filter through the ground until it eventually finds its way back into the groundwater system.

Modern-day systems employ vents and/or clean outs near the end of each line for inspection and maintenance purposes.