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Plumbing guide
Water Hammer in Peoria, AZ Homes: Causes and Fixes
A loud thump or rattle when a faucet or washing machine shuts off is called water hammer. It is more than a noise, because repeated shocks can loosen joints over time.
By the Peoria Express Plumbing team ·
What water hammer is
Moving water has momentum. When a valve closes quickly, that water stops suddenly and sends a pressure wave back through the pipes, which makes the bang you hear.
Washing machines, dishwashers and ice makers use fast-closing valves, so they are common triggers. A single-handle faucet shut off quickly can do it too.
Why it gets worse
High supply pressure makes the shock stronger. A pressure regulator that has worn out can let street pressure into the house at a higher level than the fixtures should see.
Loose pipes that are not strapped also make noise, because the pipe moves and strikes framing when the wave arrives. Sometimes the sound is partly pressure and partly vibration.
Air chambers and arrestors
Older plumbing often included short vertical air chambers behind fixtures to soften the shock. In time they waterlog and stop cushioning, and the banging starts.
A full drain can recharge them. Shut the main, open the top and bottom taps, give the pipes time to empty, then restore the supply gradually. If the noise returns, a water hammer arrestor can be installed near the problem fixture or appliance.
Check the pressure
Screw a gauge onto a hose bib to read the pressure at the house. A reading above the normal range may mean the regulator needs adjusting or replacing.
Fixing pressure often reduces the hammer along with other stress on fixtures, supply lines and the water heater.
Why pipes bang and what helps
Most cases trace to one of these four causes.
| Cause | Effect | Remedy |
|---|---|---|
| Fast-closing appliance valve | Water stops all at once | Fit an arrestor on the supply line |
| High supply pressure | A stronger shock wave | Read a gauge and check the regulator |
| Pipes that are not strapped | They knock on framing | Add padded straps |
| Air chamber full of water | No cushion left | Drain the system and refill slowly |
Secure the pipes
Look in the attic, garage and crawl spaces for pipes that rattle freely. Padded straps and brackets hold them without letting the pipe knock on wood.
Where pipes pass through framing, foam sleeves reduce contact. These are small jobs that make a big difference to noise.
Appliances that trigger it
If the noise comes from only the washer or dishwasher, inspect that connection. The supply valve may need to be opened fully, and a small arrestor on the supply line can quiet it.
A fixture valve that closes too fast or a failing cartridge may need replacement. See faucet and sink repair.
When to call a plumber
If the banging is severe, appears suddenly or comes with leaks, call. Shocks can strain joints in older pipe, and a leak behind a wall may follow.
If you suspect the supply line, read water line repair and replacement. For a hidden leak, the leak detection page covers the methods used.
Washer and dishwasher fixes
Small arrestors screw between the hose and the valve. They are inexpensive and take minutes to install.
Choose one rated for the pressure and the fitting size, and look for the ASSE 1010 marking on the package.
Noise that is not hammer
Not every bang is water hammer. A tick when the heater cycles, a hum from a pressure pump or a rattle from a loose fixture sounds different from the single sharp thump of a valve closing.
Listen for timing. If the noise comes right as a valve shuts, it is hammer. If it comes during a cycle, it is likely expansion or equipment.
Describing the sound and the timing helps your plumber find the cause faster.
How to find the source
Run each tap and appliance in turn and listen. Note which one makes the noise. Sometimes the sound travels, so the banging in a bedroom wall may come from the laundry.
Turn the main valve partway to see whether the noise drops. A change tells you pressure is part of the problem.
Mark the spot where the noise is loudest and tell your plumber.
Hot water lines and expansion
Hot lines tick and creak as they expand. This noise is different from a hammer and is not harmful. A plumber can add isolators where pipes pass through framing.
If the hot line bangs but the cold does not, check the water heater and any recirculation pump. A faulty check valve may be the cause.
Read water heater repair for related issues.
What the plumbing code says
A summary of the 2024 International Residential Code, section P2903.5, says water hammer arresters are required at quick-closing valves such as those on washing machines, dishwashers and ice makers. It says they should be listed to ASSE 1010 and installed close to the valve they protect, and that a plain capped air chamber does not count because it waterlogs over time.
That summary is paraphrased from the model code, and a city can adopt it with changes, so confirm what applies at your address with the local building department.
Common questions
Water hammer questions
Repeated shocks can loosen joints and strain fittings. It is worth fixing.
It is a compact device with a sealed chamber that soaks up the pressure wave when a valve slams shut.
A change in pressure, a worn air chamber or a loose strap can all cause new noise. A pressure reading is a good first check.
Related services
Water Line Repair & Replacement
Buried supply pipe trouble from meter to house, handled with a repair or a fresh run.
Faucet & Sink Repair
Drips, thin flow, stiff handles and leaking hose bibs, fixed at the fixture.
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Pipes still banging?
Phone the line if the noise continues. Someone on the line can hand you to a contractor who checks pressure and pipe supports.