Water Hammer Explained: Why Pipes Bang and How

A sudden banging or thudding in your walls when you turn off a tap, flush a toilet, or close a valve is usually water hammer. It’s not random: it happens when moving water is forced to stop or change direction quickly, creating a pressure surge that travels through your plumbing like a shockwave.

While the noise is often the first thing homeowners notice, repeated water hammer can stress joints, loosen fittings, and contribute to leaks over time. Understanding what causes it—and addressing the underlying plumbing behavior—can reduce both sound and risk.