Septic drainfield trench depth specification: A typical septic drainfield trench is 18 to 30 inches in depth, with a maximum soil cover over the disposal field of 36"; or per the USDA, 2 feet to 5 feet in depth.
How deep should a septic pipe be?
On average, trenches should be around 12-24 inches-deep, and wide enough to house your pipe comfortably before filling it in with soil and sod.2018-10-11