What is the minimum size for a tub shower drain?

The minimum size for a tub shower drain is 1 1/2 inches. This size is established under the Massachusetts Plumbing Code, which aims to ensure adequate drainage to prevent issues such as clogs and backups. A 1 1/2-inch drain is designed to handle the volume of water that a typical shower or bathtub might produce during use, which is essential for maintaining proper water flow and drainage efficiency.

Choosing a smaller drain size, like 1 inch or 1 1/4 inches, would not provide sufficient capacity for drainage, potentially leading to slow draining and increased risk of overflow or flooding. Additionally, a drain size of 2 inches, while it may offer more capacity, is not the minimum required. The code specifically mandates 1 1/2 inches as the standard to balance efficiency and plumbing system requirements, making it the correct answer for minimum drain size in this context.