What is the minimum size for the waste outlet of a tub serving as a drain for an overhead shower?

The minimum size for the waste outlet of a tub serving as a drain for an overhead shower is 1 1/2 inches. This size is specified to ensure proper drainage and to prevent issues such as clogs or slow drainage that may arise from insufficient pipe diameter. The larger diameter allows for the efficient removal of both water and any debris that may flow from the shower, accommodating the volume of water that can be used during a shower.

Standard plumbing codes recognize this requirement to promote effective drainage in situations where a tub doubles as a shower, ensuring that water flows freely and minimizing the risk of backflow or overflow. A 1 1/4-inch outlet may not handle the increased flow effectively, while a 1-inch outlet would be inadequate for the demands of a shower, potentially leading to drainage problems.