What is the size of the trap for an automatic clothes washer?

The correct size of the trap for an automatic clothes washer is a 2-inch trap. This size is specified because it effectively accommodates the high flow rate of water that clothes washers typically discharge, especially during the drain cycle. A larger trap allows for better drainage and prevents clogs that could arise from the volume of water and potential lint being washed away.

The 2-inch size is also in line with plumbing codes and standard practices to ensure that wastewater can flow freely without creating pressure buildup or backflow into the washing machine. The sizing is designed to ensure effective operation while minimizing the risk of creating a blockage in the plumbing system.

Other options, such as the 1 1/2-inch trap, may be suitable for other types of fixtures but are not adequate for clothes washers as they could restrict the flow of water. Options like 3-inch and 4-inch traps are typically used for larger drainage systems, such as those serving multiple fixtures or commercial installations, and are unnecessary for a standard residential washing machine setup. Therefore, the 2-inch trap is the optimal choice for the efficient drainage of an automatic clothes washer.