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Plumbing

Potential water hammer

Angela McDonald 17/09/2026 - 8.47 AM

Moved into semi detached property in May & cold water pipe banging from loft & goes through bathroom down into kitchen cupboard. Looked up in loft & most pipes are covered with pipe cover. The problem with the banging pipes only happen when neighbour has washing machine on, or probably even a tap being used / flushing loo etc.. We had Dynorod out & he stood & looked at it & said can’t help me as he said it may be water hammer but using the arrestors sometimes don’t work. Please can some help as I’m tearing my hair out with the noise. Also, this noise can happen during the night too not just during the day.

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1 Answer

ABS Plumbing

Rating: 5 out of 5

Mansfield

You undoubtedly have water hammer. Fitting an arrestor is not the best solution. The hammering is caused by a faulty or worn valve that oscillates open/shut when pressure drops elsewhere on the supply pipe. As you say the the noise starts in the loft, I'm assuming that you have a cold storage tank and a central heating tank. I suggest that you temporarily tie the ball valves in both tanks so that they can't drop and open the valve- best if the valve arm is firmly pressing against the vale itself. With that done open cold outlets, taps etc to try to recreate the sound. If that stops the problem replace one or both of the tank valves. The reason your neighbour can cause the issue is probably because you share a water supply and if they open a tap the pressure drop affects the dodgy valve in your house.

Answered17 September 2026