Could anyone give me some idea as to what is causing my problem. What happens is whenever I turn on the hot water taps, as soon as the water starts to heat up, there is a loud vibrating noise coming from the pipes, under the upstairs floorboards. This continues for up to 1 1/2 minutes, then stops. I have found that running the taps very slowly reduces the amount of times the pipes vibrates but doesn't stop it. Also if I run the bath and upstairs sink together the vibrating stops quicker, but again it does not stop it altogether and the sink flow is reduced. If anyone can give me some idea what is causing this I would be very grateful.