Thank you - I have tried this and even when only fractionally turned on (at a level where only a trickle of water comes out kitchen taps) the noise is still very loud. Didn't seem to make too much difference what ever level flow was at.
Can anyone offer some advice please? I recently replaced the ball valve arm in my cold water tank in loft as previous one had rusted up and got stuck. I used a high pressure valve - Since replacing it, every time we flush toilet, there is a whooshing sound in vertical pipes to the loft when tank...