What is water hammer and how can it be prevented during pumping operations?

• A. A minor tapping sound in the pump.
• B. A phenomenon that only occurs in large cities.
• C. A pressure surge caused by sudden valve closure; prevent by gradually opening/closing and ramping discharge.
• D. A drop in water temperature.

Answer: (C)

Water hammer is a pressure surge caused by sudden valve closure in a piping system with moving water. The moving water has inertia, so when a valve shuts quickly, it cannot stop instantly and a transient pressure wave travels through the pipe, often raising pressure well above the normal level and possibly causing banging, leaks, or damage. To prevent it during pumping operations, avoid abrupt changes in flow. Gradually opening and closing valves and ramping the pump discharge keeps the flow change gradual, reducing the pressure spike. Using soft-starts or variable-speed drives to control pump acceleration and deceleration helps as well. Additional protections, if needed, include surge tanks or air chambers, proper pipe sizing and support, and valves that close with controlled, not sudden, action. The essential idea is to manage how quickly the flow is changed to keep pressures within safe limits.