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May 2, 2017
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44
Surrey
Member Type
DIY or Homeowner
A few months back the expansion vessel from the mains water supply failed and I had the vessel and the pressure reducing valve replaced. As part of the replacement the expansion vessel was fitted with a copper tube instead of the flexible hose that was originally used.

Since the work was done we are getting a fairly loud "fog horn" noise, this only occurs when we use hot water and only after we haven't used the hot water for a period of a few hours, i.e. if it happens once in the morning it won't happen until later in the evening.

I've contacted the engineer that fitted the work and I'm hoping he can come round sometime soon to fix the problem, but is there anything that I can to that might reduce the noise. I live in a small block of flats and although no one has mentioned anything I'm fairly sure the early morning "Fog horn" noise when I jump in the shower is annoying some people.

I thought reducing the stop-cock might help but it seems to have no effect.
I'm hoping it would be fairly easy to fix, either air in the pipes somewhere or a minor adjustment on the pressure reducing valve, I'm assuming worst case the vessel or valve might have failed and needs replacing again.
 
I'm fairly confident its an unvented hot water system, the water tank has "unvented storage cylinder" on it and as far as I'm aware there isn't any cold water storage in the block of flats its fed straight from the mains.
 
It could be one of a few things but you need a G3 compliant engineer to sort this for you, it's not a DIY job i'm afraid.
Turning the stop tap down will not make any difference.
 

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