For a dishwasher, what is the trap size used?

The correct answer for the trap size used for a dishwasher is 1 1/2 inches. Dishwashers typically utilize a 1 1/2-inch trap because this size is adequate for handling the volume of water and any waste materials that are discharged during the washing cycle. This dimension strikes a balance between providing sufficient drainage capacity while minimizing the potential for clogs in residential plumbing systems.

In plumbing systems, a trap serves the critical function of preventing sewer gases from entering the living space while allowing wastewater to flow freely. The 1 1/2-inch size helps ensure that the trap can handle the discharge effectively, especially since dishwashers can produce a significant amount of water quickly. Larger traps, such as 2 inches and above, are generally reserved for larger fixtures or systems that require more substantial drainage capabilities, like floor drains or main plumbing lines, and would not be applicable for the specific needs of a dishwasher.