For interior drainage systems, the rate of flow in a fixture drain should be what?

The rate of flow in a fixture drain should be the same as the rate discharged at the fixture outlet because this ensures that the drainage system functions effectively. A well-designed plumbing system is based on the principle that the drainage from the fixture must flow freely into the pipe without risk of backflow or clogging. If the flow in the fixture drain matches the discharge rate at the outlet, it minimizes the chances of overflow and ensures that wastewater is transported swiftly and efficiently to the sewer or septic system.

Maintaining this balance is crucial in preventing issues such as slow drainage or potential blockages, which can arise if the drain cannot handle the volume being produced by the fixture. This principle is foundational in plumbing design, as it helps in achieving both optimal performance and compliance with plumbing codes.