1.1 ,This practice describes procedures for handling and installing thermoplastic pipe and corrugated pipe in septic tank leach fields, curtain drains, and from the septic tank to the leach field. Proper installation ensures that the pipe will satisfactorily convey and distribute partially treated waste water to a leaching field for additional treatment and disposal by soil absorption. The curtain or perimeter drain will function to protect the soil absorption capacity of the leach field.