Water hammer occurs when water in the hose is shut off too quickly, causing a hydraulic shock.

• A. True
• B. False
• C. Only occurs in hydrants
• D. It never jams engines

Answer: (A)

Water hammer is a hydraulic shock that happens when moving water is stopped abruptly in a hose or pipe. In firefighting, quickly shutting the nozzle or valve stops the flow suddenly, and the water’s momentum creates a pressure surge that travels through the hose, pump, and fittings. That sudden pressure spike is exactly what the statement describes, so it’s true. This phenomenon isn’t limited to hydrants; any water line can experience it when flow is halted quickly, including hoses connected to a pump. The idea that it never jams engines isn’t relevant to water hammer, which is about pressure transients rather than engine operation.