The minimum size trap arm for a bathtub is _____ inches.

The minimum size trap arm for a bathtub is 1 1/2 inches. This specification is crucial because it ensures proper drainage while preventing clogs and allowing adequate airflow in the plumbing system. A trap arm is the pipe that connects the bathtub's drain to the trap, which captures debris and prevents sewer gases from entering the home.

Sizing the trap arm correctly is essential for maintaining efficient drainage; a diameter that is too small can lead to slow drainage and increased chances of blockages due to insufficient flow capacity. The Uniform Plumbing Code defines these dimensions to ensure that fixtures perform effectively and safely, which is why the minimum size of 1 1/2 inches has been established for bathtubs. Using a larger or smaller trap arm compromises system efficiency and can lead to various plumbing issues.