I realise similar questions to this have been raised several times in the past but this seems to be a little different. I have a pressurised water system, no tank in the loft, and an oil fired boiler. Often when any tap is turned on or toilet flushed, especially first thing in the morning, a noise commences, of varying intensity, sometimes sounding almost as if a motorbike is racing through the house. The noise lasts sometimes a few seconds, sometimes a couple of minutes. This has been going on for years, several plumbers have been baffled, though unfortunately none have actually heard it as it usually happens first thing, and often will go for weeks without happening at all. We have recently ascertained that it only occurs at the times when the hot water is on, which should help diagnosis I feel. The epicentre of the noise appears to be the airing cupboard containing the tank... a 210L Santon Premier Plus unvented hot water system, and particularly the small expansion tank.
I imagine a suggestion will be to reduce the water pressure; I believe we have still heard it with pressure reduced and anyway we don't like having a feeble shower when pressure is reduced.
Any advice gratefully received. Thanks for reading this wordy post
