Knocking pipes in shower room of flat.

[PeterRayner]

I have read through previous posts about knocking pipes - none are the same as mine.
I have plumbing pipes that are not from central heating knocking 4 times a minute continuously in a shower room. The noise happens when nothing is being usedor is being used. The pressure is not great. I have had caretaker and plumber twice and spent over £200 already. The caretaker said remove paneling covering area of boxed pipes where noise came from - did that and no sign of any cause there. Then plumber and caretaker said change the ball valve/ filler ( used to be called ballcock) on WC - did that and noise actually increased from twice a minute to 4 times a minute! The caretaker also came with stethoscope to listen to pipes and said there was no knocking from communal hot water boiler. The noise now seems to be coming from another wall where the pipes are also boxed. I was thinking - should I fit a "shock arrester" or a "pressure reducing valve"? Are they the same thing? The flat next door did work in their bathroom which is next to mine but that is now rented and caretaker says I have to fix the problem from my property. What should I do? Thanks

 

[just pumps]

If you have your own cold water tank then check the ballcock on that.

 

[PeterRayner]

Thanks for your reply. Unfortunately I do not have my own cold water tank. The hot and cold water are off communal tanks and there are communal boilers for the hot water. It is a mansion flat building. The pipes are mostly copper. About 2 years ago I changed the run in my flat of the communal cold water pipe from lead to copper because it might have been leaking (actually neighbour above was leaking)- it is at ceiling height but the knocking is from floor level. The pipes revealed from removing boxing are not moving to the touch.

 

[PeterRayner]

Just to up date - I turned off the stop cock to the communal cold water supply. The knocking stopped. I have had list of qualified plumbers from Chartered Institute of Plumbers for my area and will try to get one of them to fix problem.