A plumbing system is showing signs of localized high-pressure damage, such as leaking relief valves or noisy pipes in a specific zone. During a pressure test, the plumber notes the static pressure is acceptable, but the dynamic pressure fluctuates significantly. What could be a likely cause?

Question: A plumbing system is showing signs of localized high-pressure damage, such as leaking relief valves or noisy pipes in a specific zone. During a pressure test, the plumber notes the static pressure is acceptable, but the dynamic pressure fluctuates significantly. What could be a likely cause?

Answer options:

• Insufficient water meter size. ✅ A malfunctioning pressure reducing valve (PRV) for that zone.
• The municipal water main having variable pressure.
• Excessive pipe length in the affected zone.

Correct answer: A malfunctioning pressure reducing valve (PRV) for that zone.

Explanation: If static pressure is acceptable but dynamic pressure fluctuates, especially with high-pressure symptoms, it indicates a control issue rather than a supply or sizing problem. A malfunctioning pressure reducing valve (PRV) would lead to uncontrolled pressure fluctuations downstream, causing high dynamic pressure in that specific zone. An undersized meter would cause low dynamic pressure, municipal variability would affect static pressure, and excessive pipe length would primarily cause steady pressure drop, not fluctuations.