How many fixture units does a 2" trap contribute to an automatic clothes washer?

The correct contribution of fixture units for a 2" trap servicing an automatic clothes washer is 2 fixture units (FU). Fixture units are a measure used in plumbing to describe the probable demand a fixture will place on a plumbing system. Each type of fixture has a specific rating that reflects its usage and potential for water flow.

In the case of an automatic clothes washer, a 2" trap is suitable because it can adequately handle the discharge and water management requirements of the appliance. With a rating of 2 FU, this acknowledges that while the washer does not operate continuously, its cycle involves significant water use during fill and drain cycles, which requires a designated amount of capacity in the plumbing system.

This rating is important for ensuring that the plumbing system is designed to handle the peak loads without risking backups or underperformance. Thus, using 2 FU accurately reflects the demands placed on the system by an automatic clothes washer connected through a 2" trap.