A drain field is the part of a septic system that processes and cleans the wastewater from a septic tank before it is returned to the earth. This process is known as soil absorption. Drain field trenches effectively treat liquid flowing from the septic tank. Trenches are generally 18 to 36 inches wide and up to 100 feet long. The trench contains a perforated pipe in a bed of 3/4-inch to 2-inch diameter rock covered by natural or synthetic permeable fibers. Some soil treatment systems use large plastic tubing or some other chamber wrapped with fabric in the trench in place of rock. A 6- to 12-inch deep layer of topsoil covers the trench. Sewage flows through the holes in the distribution pipe, to the rock (or tube), through the bio mat, and into the soil. Bacteria and fine sewage solids are removed or destroyed in this process. |
