What is the function of a pressure-reducing valve (PRV) in a cold water system, and when might it be required?

• A. To measure pressure in the system.
• B. To disinfect the water.
• C. To heat water.
• D. To reduce high incoming mains pressure to a safe domestic level; required when mains pressure is above system design or can cause nuisance leaks or noise.

Answer: (D)

A pressure-reducing valve lowers the incoming mains pressure to a safe, predictable level for domestic use. It acts as a regulator, keeping downstream pressure at a set value so taps, fittings, and appliances aren’t stressed, and it helps prevent water hammer and nuisance leaks or noisy operation. You’d fit it on the cold-water service entry and set it to the desired pressure (often around 3 bar) to suit the system. It’s needed when the mains pressure is higher than what the system is designed for or when that high pressure could cause leaks or noise. It’s not for disinfecting, heating, or measuring pressure.