What Is a Water Hammer and How Do You Fix It?

Water hammer is the term plumbers use for the sudden “knock,” “bang,” or “thud” that sometimes occurs in a home’s plumbing system. The noise can be startling, but the bigger issue is what it can do over time: water hammer can contribute to loosened fittings, leaks, worn valves, and even pipe damage.

It usually happens when a tap, toilet fill valve, washing machine, dishwasher, or other device suddenly stops or reduces water flow. Even a short event can send pressure waves through pipes.