High Pitched humming noise

[ericac]

I'm not sure if the boiler is making this noise, but reading afew other comments I'm beginning to think it could be. It seems to be coming mainly from near the stopcock, rather than the upsatirs combi boiler. And it goes on for hours, which is driving me mad now. I originally thought it might be the neighbours plumbing system, as we have shared mains pipes and they had new central heating system installed in the summer. This noise has been going on, getting increasingly louder, for the past month. They can't hear it though.
We have got very high pressure mains water and we've now tried turning down the mains water pressure, but that doesn't seem to have stopped it.

Could it be the pump giving up, even though the noise doens't seem be coming from the boiler?

many thanks

 

[breezer]

I am not a heating engineer or plumber, the only thing that moves a lot (not counting expansion / contraction of pipes etc) is the pump. Perhaps the pipe is rubbing against something and that is why you can hear the noise from the pump in just one place