Should the receiving pipe at an indirect drain be the same size as the supply line?

The receiving pipe at an indirect drain can indeed be smaller than the supply line. This situation arises because the purpose of an indirect drain is to carry away wastewater or overflow without directly connecting to a sanitary sewer, allowing for proper drainage without backflow issues. The smaller size allows for efficient draining while still preventing any chance of contamination from the sewer into the water supply.

In practical applications, a larger supply line facilitates a greater flow of water into a system, whereas having a smaller drain size helps to manage outgoing excess fluid properly. This design is important to meet local plumbing codes and to ensure the system functions effectively without compromising safety. Overall, the approach to sizing pipes in such installations is focused on function and regulatory compliance, not necessarily on maintaining uniformity in size between different systems.