What is the water supply fixture unit value for a bathtub with or without an overhead shower head?

The water supply fixture unit value for a bathtub, whether it includes an overhead shower head or not, is established based on the demand a fixture places on the water supply system. A bathtub has a designated value of 1.0 water supply fixture units in the International Residential Code (IRC). This value reflects the average water usage expectations and helps in calculating the overall water service requirements for both residential and commercial installations.

Using a 1.0 value for bathtubs allows for an effective plumbing design, ensuring sufficient water supply without excessive over-sizing of pipes or systems. This uniformity helps in determining the total fixture unit load when designing a plumbing system, impacting decisions regarding pipe sizing, water heater capacity, and other essential factors in residential plumbing design. Consequently, recognizing the appropriate fixture unit value is vital for compliance with plumbing codes and for efficient plumbing performance.