How are fixture unit values for special fixtures determined?

Fixture unit values for special fixtures are primarily determined based on the flow rate of the fixture. This is because fixture units are a measure used in plumbing to represent the demand or the loading of a plumbing system based on the potential flow rate that each fixture may impose on the system.

Flow rate is an essential aspect of plumbing design, as it helps to evaluate how much water will be required for each fixture in a given time frame. This, in turn, informs the sizing of pipes, the capacity of water heaters, and the overall plumbing system design. The fixture unit value takes into account the expected usage and water flow characteristics, ensuring that the plumbing system can adequately handle the maximum demand.

Understanding this principle is crucial, as it allows plumbing professionals to effectively design plumbing systems that are efficient, reduce the risk of overloading, and ensure proper water supply to fixtures as needed.