What is the minimum size plastic soil or waste pipe that may be installed underground?

The minimum size for plastic soil or waste pipe that may be installed underground is 2 inches. This specification is based on plumbing code requirements which are designed to ensure adequate flow capacity and reduce the risk of blockages in underground drainage systems.

Using a pipe that is 2 inches in diameter allows for the effective transport of waste materials and water. Smaller pipes, such as 1 1/2 inches, may not provide sufficient flow to handle typical drainage needs and could lead to issues such as backups or overflows. Larger sizes like 3 and 4 inches are permissible for underground installation, but they are not the minimum requirement; they are typically used for larger systems or where increased flow capacity is necessary. Thus, the choice of 2 inches aligns with the standard plumbing practices to ensure proper functionality of the drainage system underground.