What is a Trench Leach Field Septic System?
Septic leach trenches for disposal of septic tank effluent are one to three feet wide trenches that have up to four feet of aggregate rock with a perforated pipe installed down the middle of the trench on the top of the rock. The pipe is connected to the distribution box and the septic tank outlet pipe. Typically the aggregate rock filling the trench has a diameter of ¾ to 2-inches and has been washed to remove fines. The water leaving the septic tank drains to the perforated pipe in the trench where it leaks out the holes. It then is absorbed in the soil at the bottom and on the sides of the leach trench. Treatment of the septic tank effluent water also occurs in the soil as microbes grow and use the organics and nutrients. Physical filtering of the water also occurs in the soil.