clunking noise
everytime cold water us turned off I hear a clunk noise in boiler also hear it when my neighbour is using cold water
Replies from 3 tradespeople
Water hammer. You need a shock arrestor fitted.
Probably a washer issue on your stop tap or neighbours stop tap
That “clunk” noise you’re hearing from the boiler when the cold water is turned off—either by you or your neighbour—is most likely due to water hammer.
What is water hammer?
It’s a pressure surge that happens when water flow suddenly stops or changes direction, causing pipes to bang or make a clunking sound. It’s common in older plumbing systems or where water pressure is high.
Why is it happening near your boiler?
Your boiler might be on a mains pressure system (like a combi boiler), so any sudden changes in water flow—especially in shared or closely linked plumbing—can cause the pipes to react.
If you’re hearing it when your neighbour uses their water, it’s possible that your properties share some plumbing supply lines or that their usage is creating a pressure spike affecting your system.
