A Pressure Reducing Valve (PRV) is an Automatic Control Valve designed to reduce a higher unregulated inlet pressure to a constant, reduced downstream (outlet) pressure regardless of variations in demand and/or upstream (inlet) water pressure.

The throttled position of the main valve is controlled by an adjustable pilot valve operating in conjunction with an orifice (or needle valve). The pilot valve senses the downstream (outlet) pressure and reacts immediately as the outlet pressure increases or decreases with varying demand. The pilot senses the downstream (outlet) pressure and reacts immediately to add or remove water from the top of the main valve diaphragm assembly, allowing the valve to reposition and throttle as the outlet pressure tends to increase or decrease with varying flow demand. The pilot diaphragm will automatically sense the changes in the flow of the system as it continuously controls the main valve to throttle or to open or close and maintain the desired, pre-set reduced outlet pressure. The throttling action of the main valve provides the required reduced downstream pressure.