A plumber is evaluating an existing potable water system in a commercial building where the normal operating pressure is 480 kPa. The building owner reports frequent water hammer noises. What is the most likely cause related to pressure and flow?

Question: A plumber is evaluating an existing potable water system in a commercial building where the normal operating pressure is 480 kPa. The building owner reports frequent water hammer noises. What is the most likely cause related to pressure and flow?

Answer options: ✅ Excessive water velocity in the distribution piping.

• Installation of a pressure reducing valve.
• Insufficient water supply pressure.
• A slow-closing shut-off valve on a fixture.

Correct answer: Excessive water velocity in the distribution piping.

Explanation: Water hammer is often caused by a sudden change in water velocity, usually due to rapid closure of valves (like solenoid valves in dishwashers or washing machines) or excessive water velocity in the pipes causing high momentum. Excessive velocity (related to undersized piping or high flow) leads to more significant pressure changes when flow stops abruptly. A PRV would typically reduce pressure, insufficient supply pressure would not cause water hammer, and slow-closing valves would tend to prevent it.