Standard Practice for Installation of Thermoplastic Pipe and Corrugated Pipe in Septic Tank Leach Fields

Abstract

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. Pipe should be stored with support from a flat surface to prevent the pipe from developing a permanent set. Care should be exercised during loading, unloading, and in transit because pipe may be damaged by abrasion and sharp edges. Because thermoplastics are temporarily softened by high temperatures, care should be taken under these conditions to avoid damage during handling operations. Coiled pipe is not recommended for use in leach fields because it is difficult to install at the proper grade and alignment; it is acceptable with special equipment installation. Pipe can reach comparatively high temperatures when exposed to the sun and this reduces the pipe stiffness appreciably. Therefore, precautions must be taken to prevent the impact of sharp or heavy objects, the sudden imposition of heavy overburden or excessive pull on such pipe. The pipe regains full strength and stiffness as the temperature decreases to that of the soil; this will normally require about five minutes. Care in handling and installation should be exercised under low-temperature conditions to avoid damage. As temperatures decrease, some types of pipe tend to become more brittle and less flexible.