What is the purpose of fixture units in plumbing?

The purpose of fixture units in plumbing primarily revolves around assessing the drainage capacity and load on plumbing systems. Fixture units provide a standardized measurement that represents the potential demand a fixture may place on the drainage system during peak usage. Each type of fixture, like sinks, toilets, and showers, is assigned a certain number of fixture units based on its expected flow characteristics.

By using fixture units, plumbers can calculate the necessary size of drainage piping and design the overall plumbing system to ensure that it can adequately handle the anticipated wastewater flow. This information is crucial for preventing issues such as backups, overflows, or insufficient drainage, which can lead to costly repairs and health hazards. Understanding the concept of fixture units helps in creating an efficient and effective plumbing design that meets local codes and regulations.