What is 'water hammer' and how can it be mitigated during suppression?

• A. Pressure surge when quickly closing a valve or stopping large flow; mitigate by closing valves gradually and manage pump operations.
• B. A phenomenon where water missiles cause injuries.
• C. A method to increase pump discharge.
• D. A type of protective equipment.

Answer: (A)

Water hammer is a pressure surge that happens when moving water is suddenly stopped or its flow is rapidly interrupted, such as when a valve is closed quickly or a large flow is halted. The momentum of the moving water creates a shock wave that travels through the piping, which can spike pressure and risk damaging pipes, fittings, and equipment like pumps and hoses. To mitigate this during suppression, operate valves and pumps smoothly—avoid snapping closures or abrupt halts of flow. Close hose outlets gradually, coordinate pump shutdowns with controlled valve closures, and maintain a deliberate sequence of actions to minimize how quickly water velocity changes. Using gradual closures reduces the rate of pressure rise, protecting the system. The other options describe things unrelated to this hydraulic phenomenon, so they don’t fit.