What is the function of a pressure-reducing valve (PRV) in a cold water system, and how might it be implemented to balance pressure on multi-story buildings?

• A. It reduces the supply pressure to a set level; installed on feeders to individual floors or zones to maintain balanced pressure.
• B. It increases pressure to the top floors only; installed upstream of the main shut-off.
• C. It acts as a backflow preventer; installed at each fixture.
• D. It filters impurities; installed at main entry.

Answer: (A)

A pressure-reducing valve lowers incoming water pressure to a chosen operating level, protecting piping and fixtures from high pressure and reducing issues like water hammer. In a multi-story building, supply pressure from the street can be high and can vary between floors, which can cause overpressure on lower levels and inadequate flow on upper levels. Placing a PRV on each floor’s feeder (or on a zone feeder) and setting it to a standard target pressure creates balanced pressure throughout the building so every floor receives similar flow without overstressing pipes. The device does not increase pressure, and it is not a backflow preventer or a filter, so those roles are handled by other components in the system. For maintenance and adjustment, include isolation valves and set the PRV to the needed pressure range (commonly around 40–60 psi, depending on local codes and fixture requirements).