I had screeching pipes & water hammer when the taps were turned off (straight after a new bathroom was installed - didn't have it beforehand). I then had a pressure regulating valve attached as well as a water hammer arrestor. However, now when the taps turn off there is a drilling sound either immediately after or anything between 0-20 seconds after turning the taps off which is loud & causes a noise throughout the flat!
When I watch the pressure valve after turning the tap off, it suddenly jumps from around the number 3 to 4 and the needle flickers whilst the noise happens. It seems the pressure suddenly jumps up which causes the noise....how do I fix this please as I already have a water hammer arrestor which is supposed to absorb this extra pressure...right? My water pipes are connected with 2 other flats so every time they use their taps throughout the night we get the noise! Thanks for any advice.