How to Fix Water Hammer in Pipes

Water hammer can be fixed by installing air chambers, water hammer arrestors, or adjusting water pressure. Most cases resolve with simple arrestor installation at problem fixtures.

  1. Pinpoint the Banging Source. Turn on different fixtures one at a time to pinpoint where the banging occurs. Water hammer typically happens when you quickly shut off faucets, flush toilets, or when washing machines and dishwashers cycle. Listen for the loudest banging sounds to locate the problem area.
  2. Measure Water Pressure First. Attach a pressure gauge to an outdoor spigot or laundry room faucet. Normal residential water pressure should be between 40-60 PSI. If pressure exceeds 80 PSI, install a pressure reducing valve at your main water line. High pressure is a common cause of water hammer.
  3. Add Shock-Absorbing Arrestors. Shut off water supply to the affected fixture. Disconnect the supply line from the fixture. Thread a water hammer arrestor onto the shut-off valve, then reconnect the supply line to the arrestor. These small devices absorb the shock waves that cause banging. Install one for both hot and cold lines if both cause problems.
  4. Build Custom Air Chambers. If your home lacks existing air chambers, install them near problem areas. Cut into the water line and install a tee fitting. Attach a 12-inch vertical pipe segment capped at the top. This creates an air cushion that absorbs pressure surges. Air chambers work best when installed as close as possible to quick-closing valves.
  5. Restore Air Chamber Function. Older homes may have air chambers that have become waterlogged. Turn off your main water supply and open all faucets to drain the system completely. Close all faucets and turn the water back on. This refills the air chambers with air instead of water, restoring their shock-absorbing function.
  6. Lock Down Vibrating Pipes. Check exposed pipes in basements, crawl spaces, and utility rooms for loose mounting brackets. Tighten existing brackets and add new ones every 6-8 feet for horizontal runs and every 8-10 feet for vertical runs. Use cushioned pipe hangers to reduce vibration transmission to the house structure.