What are fixture units?

Fixture units represent a measure of the load that plumbing fixtures place on a drainage system. This concept is essential for plumbing design because it helps determine the adequate sizing of drainage systems to handle the wastewater generated by various fixtures. Each type of fixture, such as sinks, toilets, or showers, has a specific assigned value in fixture units based on its expected usage and the associated flow rate.

By quantifying the load using fixture units, plumbers and engineers can ensure that the drainage system is designed with sufficient capacity to handle peak usage levels, avoiding potential backups or overflows. This calculation is crucial for maintaining efficient and effective plumbing systems, as it accounts for the varying usages of fixtures under normal operating conditions.