How to Handle Water Hammer

The annoying sound of water hammer can be more than just an inconvenience. Learn what to do about water hammer before your plumbing is damaged.


  • Step 1: Install a water hammer arrester behind the valve or faucet that is causing the water hammer. A water hammer arrester is an air-filled tube that connects to the supply pipe. It allows the pressure in the pipe to dissipate into the air instead of exploding in the pipe.
  • TIP: Arresters may be difficult to install if the problem pipe is inside a wall to supply a dishwasher or refrigerator.
  • Step 2: Change all of your fixtures -- or at least the offending one -- to a low-flow fixture. Low-flow fixtures use less pressure, so the flow of water to the valve won't be fast enough to cause water hammer.
  • FACT: Hollowed-out logs were used as water pipes in America in the late 1700s to early 1800s.
  • Step 3: Install an expansion tank, which contains a rubber diaphragm that cushions the shock wave of water hammer.
  • Step 4: Secure your pipes -- especially along particularly long, straight runs -- to reduce water hammer. Copper water pipes should be strapped to ceiling joists at 4-foot intervals to reduce rattling.
  • TIP: You can check your home's water pressure with a gauge available at hardware stores.
  • Step 5: Replace the pipes leading to the valve. If you increase the size from your 1/2-inch copper supply pipes to 3/4-inch pipes, the water velocity will slow and the chances of experiencing water hammer will be greatly reduced.
  • Step 6: If your water pressure is excessively high -- between 60 and 80 pounds per square inch, or PSI -- you can install a pressure regulator to decrease the pressure. If you reduce the pressure to between 40 and 50 PSI, you will still have sufficient water pressure in your plumbing.
  • Step 7: Reduce the pressure in your pipes. Water hammer occurs when water traveling at a high rate of speed is suddenly stopped, usually by closing a valve or faucet. If the pressure is reduced, the water's velocity will slow, and the shock wave caused by closing the valve won't be large enough to cause a noise.

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