Pipes bang or hammer when taps or appliances shut off

visibilityHow to check

1. Run several different taps and note whether the bang shows up in more than one place — a system-wide hammer that has worsened over years points to waterlogged air chambers rather than a single loose pipe or appliance.
2. Locate your main water shutoff now, before you need it — usually where the supply enters the basement or a utility room, or at the water meter. You'll need to reach it to recharge the chambers.
3. If draining and recharging the system quiets the hammer (see the fix), waterlogged chambers are confirmed. If the noise returns quickly, the home may lack air chambers entirely and need an arrestor instead.

handymanHow to fix it

Shut off the main, open the highest and lowest taps in the house to drain all the water (and the air-filled chambers refill with air), then close the taps and slowly restore the main. If the hammer returns, install a water-hammer arrestor at the supply valves nearest the offending fixture or appliance.

1. Find and close the main water shutoff. Note the flooding risk if you can't locate it — do not start until you know where it is.
2. Open the highest tap in the house (an upstairs faucet) and the lowest (a basement laundry tap or an outside bib) and let everything drain fully — this empties the waterlogged chambers so they refill with air.
3. Flush each toilet once while draining to clear the tanks, then close all the taps you opened, starting from the lowest.
4. Slowly reopen the main and let the system refill; the air trapped in the chambers should now cushion the shock. If the bang comes back within days, the home likely lacks working chambers — install a water-hammer arrestor at the culprit valve instead.