A water hammer device is installed as close as possible to the valve causing the problem.

• A. Pressure reducing valve
• B. Air chamber
• C. Water hammer
• D. Check valve

Answer: (C)

When a valve shuts quickly, the moving water can’t follow, creating a pressure surge known as water hammer. Placing a water hammer arrestor right at the valve gives the surge an immediate cushion to compress, absorbing the energy at the source and keeping the spike from traveling far down the line. The closer the arrestor is to the valve, the more effective it is at protecting pipes, fittings, and fixtures and at quieting the banging. A pressure reducing valve changes steady downstream pressure, not the transient surge; a check valve prevents backflow but doesn’t absorb the shock; an air chamber can serve as an arrestor but can lose its air over time, making it less reliable than a purpose-built water hammer arrestor.