What happens in a centrifugal pump when the nozzle is shut off quickly?

When the nozzle of a centrifugal pump is shut off quickly, it creates a sudden change in flow, which in turn generates a pressure wave. This pressure wave travels through the system, and because of the nature of the hydraulic setup, it will ultimately reach the water main.

The reason the correct answer is linked to the water main is due to the dynamics of water flow and pressure within a closed system. When the flow is abruptly halted, the momentum of the moving water generates a high-pressure surge that travels back towards the source of the water supply. This surge will continue until it reaches a point of resistance, which in many scenarios will be at the water main.

This phenomenon is crucial in understanding how pressure surges can affect water systems, as it illustrates the importance of considering the effects of rapid flow changes, such as valve closures, which can lead to potential damage if not properly managed. Understanding these dynamics helps in the design and operation of fire suppression and water delivery systems to prevent issues such as water hammer and other pressure-related failures.