What is the drain size for a combination tub and shower?

The drain size for a combination tub and shower is 1 1/2 inches. This size is recommended because it provides adequate drainage for both the bathtub and the shower functions without being prone to clogs or slow drainage.

In plumbing systems, particularly for fixtures that handle significant water flow like a tub and shower combo, the 1 1/2-inch drain size effectively balances flow rate and pipe capacity. The larger diameter allows for efficient removal of water, minimizing the risk of standing water and ensuring compliance with plumbing codes that help maintain functionality and safety in residential systems.

Larger drains, such as 2 inches or 3 inches, are typically reserved for main drainage lines or more extensive systems, whereas smaller drains, like 1 1/4 inches, are generally inadequate for this specific application due to their limited capacity to handle water volume effectively.