What does a drainage system begin at?

A drainage system begins at the flood level rim, which is the point at which the plumbing fixtures are designed to prevent overflow and backflow. This level is critical because it establishes the maximum height to which water can rise in a fixture before it spills over, thus determining the effective drainage and preventing any potential for flooding. Each fixture’s drain must be designed to carry wastewater away quickly and efficiently from the flood level rim, ensuring that the drainage system operates correctly.

Understanding this concept is essential for plumbing professionals, as it guides the installation and maintenance of fixtures and their connections to the drainage system. The flood level rim also relates to how systems must be properly vented and configured to avoid issues like siphoning or backpressure, which can affect system performance. This foundational knowledge supports the effective design and troubleshooting of plumbing systems.