Drain fields, also known as leach fields, are created over determined areas of land where waste water can be collected and naturally filtered through trenches, layers of soil and a series of pipes. Sandy or loamy soils are often used because of their filtration ability. After the waste water percolates through the soil, moving through trenches and pipes, it is gathered by built-in drains and funneled to a collection area where the effluent is further treated.
Things You Will Need
Thin cloth, such as linen
Credit: band of land image by Chris Holmes from Fotolia.comMeasure the drain field per the specifications set forth by the county environmental governing body's request. Septic tank sizing is determined by usage, with at least a 30-hour sewage treatment retention time considered adequate. Use a soil engineer if the ground bedrock is unsuitable soil, less than four feet below the proposed leach field, or if the ground slope is in excess of 30% in the area of the proposed for the leach field, suggests NMED Liquid Waste Program Public Outreach and Training.
Test the soil, using a percolation test, with the county environmental board. This identifies the filtration potential of the area considered for a drain field. Once all is approved, obtain the proper permits before you begin.
Dig trenches for your drain field with an earth-mover or backhoe. From 3 to 4 feet in depth, the trenches should be deep enough to filter sewage material adequately. Make each trench with a subtle downward slant, away from the home. Make the slant no more than one forth of an inch per wight feet of pipe to avoid blockage or backup at the end of the pipe.
Add a 1-foot layer of gravel along the length of the trench or trenches. Top the gravel with the perforated pipe, then use a clamp to attach the pipe to your septic tank drain. For added filtration, add up to 1 1/2 feet of gravel under the pipe.
Add an additional half inch of gravel over the perforated pipe and around the pipe to secure it in place. Add a thin liner over the top of the gravel and pipe to prevent soil or other debris from entering the trench. Refill the trenches with the soil that was taken from the area until the area is flush and back to its original appearance.
Tips & Warnings
Different counties have different codes and tests that must be met before obtaining a permit for a drainage field. Call your local, county environmental department to get the codes and information you need to locate the right area for your drainage field.