Knocking/water hammer?

Kai77

I live in a first floor Victorian conversion flat.

The neighbours downstairs are doing major work.

In the past couple of days, I've been hearing a kind of knocking sound (a bit like when a window is open and a shut door makes a sound against the wind) whenever I run a tap.

It's never happened before. The neighbour downstairs and I both have mains taps in the shared hallways, they've actually turned mine off before by accident. 

Is it possible that my pipes have become loose while they've been working on their own? My water pressure isn't particularly high as it is because the water has to run from downstairs up to mine.

AlexMac

I experience a single loud clonk whenever I turn off one tap  - the mixer tap in my kitchen , and that happens only when the tap is turned to hot. It doesn’t happen when the tap is in the cold position, nor if I close down the tap very gently. 

 I know exactly what it is; a loose, or rather, unsecured hot water supply pipe in the ceiling void below the floorboards of the hall immediately above.  Both hot and cold pipes run about 3 metres across this hall from the hot water storage tank, before descending a further couple of metres in a conduit in the kitchen wall to supply the sink, dishwasher etc. 

I know it’s loose because when lifting and re-securing a few loose floorboards prior to carpeting some years ago, I noticed that both pipes were “floating”. I had a couple of spare clamps, so I secured one (the cold supply) to the closely adjacent joist, but stupidly didn’t bother working out how to fasten down the parallel hot pipe, before closing down the flooring! I think I even recall that both pipes used to clunk when I suddenly changed the water pressure by slamming the tap off. 

Not that this helps you of course, unless you (or a plumber) can pinpoint and access the site of the noise? What surprised me was that in my case, the knocking is some 5-6 metres away from the tap whose sudden closure causes it?

Kai77

Thanks, this has been happening with both taps, whenever I run them, like you though, far away from the source. I do suspect the pipes have become loose but given the building work and shared location of the tap and pipes, I wonder if the builders have shifted something during the work.

Liverpool85

In my house I can stop the water hammer by partly closing the stop tap- I still get fine pressure. 

I wonder if they closed you’re and then fully opened it, whereas before it may have not been fully open