Pipes banging or knocking
A loud bang when a faucet, washer or dishwasher shuts off is called water hammer. It's more than annoying: it can loosen joints over time.
What causes it
Water moving through a pipe stops suddenly when a valve closes quickly, and the shock wave rattles the pipe. Washing machines and dishwashers with fast-closing valves are common triggers.
Things to try
- Note which fixture or appliance causes it. That tells a plumber where to look.
- Check whether pipes in the crawl space or basement are loose. Secure them with pipe straps.
- Older homes may have air chambers that have filled with water. Shutting off the main, opening the highest and lowest faucets to drain the lines, then refilling can restore them for a while.
Permanent fixes
- Water hammer arrestors installed at the washer or the noisy fixture.
- A pressure reducing valve if household pressure is too high.
- Better pipe support where runs are long and loose.
Ticking or creaking as hot water runs is different: that's pipes expanding, and it's usually harmless.