Firefighter Practice Exam

What can occur if the flow of water is suddenly stopped in a firefighting system?

1. Pressure drop

2. Water hammer

3. Vapor lock

4. Back pressure

The correct answer is: Water hammer

When the flow of water is suddenly stopped in a firefighting system, water hammer can occur. This phenomenon is caused by the rapid deceleration of the moving water, leading to a shock wave that travels back through the pipes. As the water comes to an abrupt stop, the energy generated by the moving water has nowhere to go and creates a high-pressure surge that can lead to noise, vibration, and potentially damaging effects on the piping system. This can cause joints to fail, pipes to break, or fittings to loosen, which can complicate firefighting efforts and lead to additional repairs. In contrast, while a pressure drop may happen in other scenarios related to water flow, it is not the direct result of stopping the flow suddenly. Vapor lock typically occurs in systems with fluids that can vaporize and is more relevant to pumps rather than the immediate water flow dynamics in piping. Back pressure involves a buildup of pressure against the flow of fluids, distinct from the sudden stopping of flow that leads to water hammer.