Recently the GF had significany rennovations done to her home. It involved a new bathroom. The fixtures remained basically in the same locations, but the plumbing had to be adjusted very slightly. New taps, nozzles, etc. There were no signifant changes made that I amaware of.
The issue is when she turns off the COLD water quickly there is a thump-thump behind the shower wall, but it does not repeat itself. It is difficult to tell, but it seems to come from above the faucet assembly. The water feeds from below.
The same happens if the sink in this bath and the adjoining bath or the toilet flow stops suddenly - it seems to be the cold water in all cases.
I do not think it happens with hot water, nor does it happen if the water is turned off more gradually.
Is there a possibility it could be the shower valve assembly, or a loose pipe? I am hoping there is some way to try to repair it without going through walls.
Any imput/observations/approaches to try/or further diagnostic methods to narrow it down more would be greatly appreciated!!!!