How to Build a Septic Drain Field

A septic drain field consists of perforated pipes set down in trenches that remove foreign matter and contaminants out of the liquid waste flowing from a septic tank. The liquid waste then seeps out into the ground and is filtered by the earth before reaching the water table. Before you build a septic drain field, check your local ordinances and obtain permits or a site inspection.

Items Needed:

• Shovel


• Measuring tape


• Gravel


• Perforated pipe


• Clamps


• Drain field fabric

1. Choose a location for your drain field. The field will have to be fairly close to the septic tank and at a minimum distance of 10 feet away from your house, garden or any water source.


2. Dig four 25 feet long trenches or two 50 feet long trenches. Dig each trench 3 to 4 feet wide and 3 to 4 feet deep. Dig the trenches at a 1/4 inch slant for every 8 feet. If the trenches are too tilted, the water will settle at the bottom of the trench and the sewer will back up.


3. Place 1 to 1 1/2 feet of gravel in each trench to help with drainage under the pipe.


4. Lay perforated pipe on top of the gravel in each trench. Place a clamp on the pipes at the septic tank drain to keep the pipes from slipping.


5. Shovel 1 to 3 inches of gravel over the pipe in each trench and let the gravel work its way down around the pipe. 


6. Place drain field fabric over the top layer of gravel to deter dirt and debris from blocking the drainage system.


7. Fill the rest of the trench with backfill and level the entire drain field. After the ground settles in a few weeks, you can add more dirt and level the drain field again.