Some kind of water hammer??

[webrits]

OK, I seem to have a weird water hammer (??) in the house.
It's just a small 'knock' every 10 seconds, like clockwork. It never speeds up or slows down and happens maybe 50% of the time. It can only be heard if all is quiet, especially at night, but stops for a short time if a tap is opened.
Pretty sure it's on the mains cold as I can actually feel it on the cold water pipes.
Water pressure is v high here, >10bar !

Could it just be a worn stopcock? I'm just surprised that it's such a regular 'knock'.

If it the stopcock, there's another problem. Mains water in is 15mm copper, then looks like this has a coupler either end, taking it to 20mm... not 22mm. Are 20mm stopcocks available anywhere? I can't seem to find any...

 

[webrits]

Can anyone help me, please?

 

[Harry Bloomfield]

My guess would be a toilet cistern or tank (central heating?), where the float valve is set too high, passing a little water and is overfilling/over spilling, via the over flow.

Do you have a water meter and could check the reading last thing at night, then again before any water is used next day?

Could you maybe turn the water completely off on a night, to just check the noise does stop with the water off?

Stopcocks don't usually make any noise, apart from when water is flowing.

 

[webrits]

Thanks Harry,
I've tried isolating each toilet in turn and it still occurs. CH is a combi, so no tank.
Don't have a water meter either I'm afraid!
I'll maybe try closing the stopcock completely tonight, see if that stops it.

Thanks

 

[Harry Bloomfield]

CH is a combi, so no tank.

TRV's on radiators have been known to make a noise, does you heating run at night?

 

[webrits]

No, the heating is off at night. Plus I can feel the knock through the cold pipes and not the heating system.

 

[Harry Bloomfield]

No, the heating is off at night. Plus I can feel the knock through the cold pipes and not the heating system.

It could be a neighbours system causing water hammer, if it is not your system.