Tutorial - Leach Pits
A single leach pit consists of a perforated concrete (or plastic) chamber placed on a layer of leach stone in a pit, about 3 times as wide as the chamber. The pit is then filled with leach stone up to the top of the chamber. A 3-inch layer of pea stone is then placed over the leach pit and leach stone to prevent topsoil from mixing with the leach stone. When there is more than one leach pit, a distribution box (D-box) is used to split the flow to the different pits.
Figure 2 - Septic System with Leach Pits