We have a 1960’s bungalow and the mains water supply comes in to an under-floor void. It then runs in soft copper, which is just laying on the over-site concrete, across to where there was originally an airing cupboard with a hot water cylinder.

It goes up through the floor into this cupboard where there is a conventional stop cock but then goes straight back down and runs in the under-floor void to the bathroom and en-suite.

As some point the old hot water cylinder was removed and a combi-boiler installed and to get a cold water supply for this a tee was inserted into the incoming main before any stop-cock. Copper pipe runs up from this tee to another stop-cock and then on to the cold tap in the kitchen as well as feeding the combi-boiler. The pipe work isn’t very well supported but we’ve had no problems for the 6-years we’ve lived here.

Last week we had a new combi-boiler fitted and now get a loud bang when any of the taps (hot or cold) are operated which I assume is water hammer.

The guy who installed the boiler simply said he hadn’t touched any of the other pipework and had fitted a shock arrester in the cold feed just below the boiler. He did however suggest fixing the old pipework more securely.

I can’t see how anything he’d done could have caused the problem but it wasn’t an issue before.

Any suggestions?

John.

Fixing the pipes down will help but the easiest fix (at least when I had the same problem) was to close the stop cock a little. You may need to experiment with it a bit to get the desired affect.

A small change in overall water pressure reduced the water hammer by 99% and it took about 5 seconds to do.

Good luck - I hope it works as well for you as it did for me

He's probably opened the second stopcock you mention fully, after connecting the new boiler, where as previously may be it was shut down a little to reduce flow.