What is water hammer and how can it be prevented?

• A. A pressure surge caused by a sudden change in flow.
• B. A pressure surge caused by a sudden change in flow; prevent by opening valves slowly, using surge suppressors, and gradual throttle changes.
• C. A routine method for priming a pump.
• D. A device used to measure discharge pressure.

Answer: (B)

Water hammer is a pressure surge that occurs when flow is changed suddenly, such as when a valve is closed quickly or a pump stops abruptly. The moving water has inertia, so stopping or rapidly slowing it creates a shock wave in the piping, causing a sudden spike in pressure that can damage pipes, joints, and equipment. To prevent it, ease changes in flow: open valves slowly, use surge suppressors or arrestors to cushion pressure waves, and make throttle changes gradually when starting or stopping pumps. This combination addresses both the cause and the mitigation of the surge. A routine priming method and a device for measuring discharge pressure don’t define water hammer or its prevention, so they aren’t correct in this context.