Pressure Reducing Valve Sizing Calculator



Enter the appropriate information in the boxes below.

* Required Fields

Select PRV Model*
Flow Target* GPM
Inlet Pressure* psi
Set Outlet Pressure* psi
Minimum Outlet Pressure at Target Flow* psi

Watts product specifications in U.S. customary units and metric are approximate and are provided for reference only. For precise measurements, please contact Watts Technical Service. Watts reserves the right to change or modify product design, construction, specifications, or materials without prior notice and without incurring any obligation to make such changes and modifications on Watts products previously or subsequently sold.

The UPC and the IPC dictate velocity limitations in water supply systems and plumbing engineers recommend, to prevent erosion corrosion, the cold water velocity limit for copper is about 8 feet per second (fps), while the hot water velocity limit for copper is about 5 fps. However, the hot water velocity limit of 5 fps is based on a maximum temperature of 140°F. Per the Copper Tube Handbook (, once the fluid temperature exceeds 140°F, the velocity needs to slow down to 2 to 3 fps, as the water becomes more aggressive the hotter it becomes.

To slow the velocity of water in a given pipe, either (a) the flow rate must reduce or (b) the pipe must get larger. The values in the UPC are better defined for the specific application. It is important to note that other factors may contribute to velocity limitations, such as acoustical requirements for sound-sensitive areas and corrosion and erosion in piping due to water quality.

In sizing any water distribution system, work with the project engineer to understand the building-use type, occupancy type, and quantity of people that will be occupying the building. for the required quantity of plumbing fixtures and appliances, so that valve and pipe sizing can then be determined using the appropriate plumbing code section.