What size P-trap shall be installed on the lower terminus of the building drain when wastewater from a swimming pool goes into a public sewer?

The appropriate size for the P-trap installed on the lower terminus of a building drain for wastewater from a swimming pool discharging into a public sewer is 3 inches. This size is typically dictated by plumbing codes that govern the safe and effective drainage of wastewater.

A 3-inch P-trap is designed to handle the volume and flow of water that would be expected from a swimming pool, ensuring that the system can effectively manage both the wastewater and prevent any potential for clogs. It also helps in maintaining the proper water seal necessary to prevent sewer gases from entering the building.

In the context of building drains, where the discharge is substantial, using a trap that is too small could lead to drainage issues and backups, which is why the sizing is critically important. The installation of a 3-inch P-trap aligns with industry best practices and regulatory requirements, making it an essential consideration for contractors to ensure compliance and functionality in swimming pool drainage systems.