What causes water hammer in a plumbing system?

Water hammer is a phenomenon that occurs when there is a sudden interruption in the flow of water, leading to pressure surges that can cause banging or knocking sounds in the pipes. The primary cause of water hammer is the abrupt closure of a valve. When a valve is suddenly shut, the moving water is brought to a rapid stop, creating a shock wave that travels through the plumbing system. This surge of pressure can result in the familiar hammering noise and can potentially damage pipes, fittings, and appliances.

In contrast, slow closing of a valve can mitigate the effects of water hammer because it allows water to decelerate gradually rather than coming to a sudden halt. While a sudden increase in water pressure can lead to problems in a plumbing system, it is not the direct cause of water hammer itself. Excessive water flow can contribute to overall system strain but is not a direct trigger for the hammering effect seen during rapid valve closures. Understanding these dynamics is crucial for preventing water hammer and ensuring the longevity of plumbing systems.