Quick answer
Pipes that bang when a faucet, toilet or washer shuts off are showing water hammer: water stops suddenly at a closing valve and the pressure wave knocks the pipe. Test the water pressure (household pressure is usually 40 to 80 psi), drain the system to restore air chambers, and look for loose pipe straps. The lasting fix is a water hammer arrestor near the fast-closing valve, or a pressure-reducing valve if pressure is high. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 3, 2026· Next review May 2027
Pipes that bang when a faucet closes or a washer finishes filling are most often showing water hammer: moving water stops suddenly at a valve, and the pressure wave slams the pipe against framing. Other noises, such as rattling, whistling or ticking, point to different causes, and some are worth a plumber's visit.
Match the Noise to the Cause
| Noise | When you hear it | Likely cause |
|---|---|---|
| Loud bang or thud | Right after a faucet, toilet, washer or dishwasher shuts off | Water hammer |
| Rattling | While water runs | Loose pipe straps |
| Whistling or squealing | While water runs | Worn valve, washer or pressure regulator; high pressure |
| Ticking or creaking | As hot water runs, then again as it cools | Hot pipe expanding against wood |
| Humming | Constant, with a well | Pump or high pressure |
Things a Homeowner Can Check
- 1Test the water pressure. A gauge that screws onto a hose bib costs little. Household pressure is usually set between 40 and 80 psi; above 80 makes water hammer much worse. A pressure-reducing valve near the main fixes that.
- 2Drain the system to restore air chambers. Older homes have short capped pipes that hold a cushion of air. Close the main, open the highest and lowest faucets until the pipes drain, then close them and reopen the main. It often quiets the bangs for a while.
- 3Find the loose strap. In an unfinished basement or crawlspace, look for a pipe that moves when water runs.
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
The Usual Plumber's Fix
The lasting fix for water hammer is a water hammer arrestor: a small sealed chamber installed near the valve that closes fast, usually the washer, the dishwasher or the ice maker supply. If the pressure is high, the fix is a pressure-reducing valve or replacing a failed one.
Why Not to Ignore It
Repeated hammering stresses joints and fittings, and a banging pipe on a supply line can loosen a connection over time. See low water pressure for pressure problems in the other direction.
When to Call
Call if the pressure is over 80 psi, if the banging started suddenly, or if you see drips at joints near where it bangs. Plumber labor at regular hours runs $45 to $200 an hour, about $100 on average, according to Angi. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
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Frequently Asked Questions
Why do my pipes bang when I turn off the water?
That is water hammer. Water moving through the pipe stops suddenly at a closing valve, and the pressure wave knocks the pipe against framing.
Is water hammer dangerous?
Repeated hammering stresses joints and fittings and can loosen a connection over time. It is worth fixing, especially if pressure is above 80 psi.
How do plumbers fix water hammer?
With a water hammer arrestor installed near the fast-closing valve, often the washer or dishwasher supply, or a pressure-reducing valve if household pressure is high.
Sources
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Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.