A homeowner complains of fluctuating water pressure and a 'hammering' noise when faucets are quickly shut off. After checking the main pressure regulator, which is set correctly at 345 kPa, the plumber suspects an issue related to rapid pressure changes. What plumbing component is most likely missing or malfunctioning in this scenario?

Question: A homeowner complains of fluctuating water pressure and a 'hammering' noise when faucets are quickly shut off. After checking the main pressure regulator, which is set correctly at 345 kPa, the plumber suspects an issue related to rapid pressure changes. What plumbing component is most likely missing or malfunctioning in this scenario?

Answer options: ✅ A water hammer arrestor.

• A backflow prevention device.
• A pressure reducing valve (PRV).
• A thermostatic mixing valve (TMV).

Correct answer: A water hammer arrestor.

Explanation: Water hammer, characterized by banging noises when faucets are closed, is typically caused by the sudden stopping of water flow, and it is mitigated by water hammer arrestors. Backflow preventers protect against contamination, PRVs reduce incoming pressure, and TMVs mix hot and cold water to a safe temperature.