Banging or knocking in water pipes is often caused by water hammer, which happens when flowing water is stopped suddenly. Loose pipe clips, high water pressure and heating pipes expanding can also cause noises. The type of sound, and when it happens, gives useful clues about the cause.
Water Hammer from Valves Closing Quickly
Water moving through a pipe carries energy. If a valve shuts very quickly, that moving water has nowhere to go, and it sends a shock back along the pipe. The result is a loud bang or thud, sometimes followed by a shudder.
Washing machines and dishwashers are common causes. Their valves open and close quickly as they take in water, so you may hear a bang partway through a cycle. Quarter-turn taps, which go from fully open to fully closed with a short turn, can do the same.
Toilet cistern fill valves can also cause knocking as they close. Some older types shut sharply or chatter as the water level rises. Noting which tap or appliance was just used when the bang happened can help narrow things down.
Loose Pipes and High Water Pressure
Pipes should be held firmly in place with clips or supports. Over time, these can loosen or go missing, especially where pipes run under floors or in cupboards. A loose pipe can move and knock against joists, walls or other pipes when water flows or stops.
High water pressure can make water hammer worse, because the water is moving with more force. It can also put extra strain on taps, valves and appliances. Checking whether pressure is the cause is a job for someone who can test it properly. Our page on water pressure problems explains more about how pressure can affect a home.
Air trapped in pipes can also cause noises. You may notice spluttering taps or knocking as air pockets move through the system, often after the water has been turned off and back on.
Ticking and Creaking from Heating Pipes
Not all pipe noises come from the cold supply. Central heating pipes get warmer and then cool down, and they expand and contract as they do. This can cause ticking, creaking or cracking sounds, especially where pipes pass through tight gaps in floors or joists.
These noises often follow the heating timer, starting when the heating comes on and stopping once the pipes settle. They are usually a nuisance rather than a danger, but they can still be worth looking at if they are loud.
When to Get the Noise Looked At
Occasional noises may not be a big concern, but frequent or loud banging is worth checking. Repeated water hammer can put strain on joints and fittings over time. If knocking comes with leaks, damp patches or changes in pressure, it is best not to ignore it.
Getting to the cause often means ruling out one possibility at a time, which is where help with plumbing fault finding can be useful.
If noisy pipes are keeping you up at night in Swindon, Emergency Plumber Swindon is happy to talk it through. Call us on 01793 569521.