In plumbing, how many units is the equivalent of a private water closet fixture with a 3" trap?

A private water closet fixture with a 3-inch trap is typically assigned a value of 4 fixture units. In plumbing design, fixture units serve as a way to quantify the demand that a particular plumbing fixture places on the drainage system. The sizing of the drainage system is dependent on the total number of fixture units within a system to ensure efficiency and effectiveness in handling wastewater.

Assigning 4 units to a private water closet reflects its expected usage and hydraulic load, which factors into designing the plumbing system for adequate waste transport and venting. Understanding the concept of fixture units is essential for any plumbing contractor, as it helps in ensuring that systems are not only compliant with code but are also efficient in operation.