Strange problem - mains water running for 10 secs every few mins

[Adam Jenkins]

Hi,

Got a strange issue and hoping someone has some ideas please.

The other day I needed to switch off the stopcock to work on my toilet. Water was off for an hour or so and since then there is a strange noise every few minutes. It sounds like water running in a pipe and is coming from the same area under the sink as the stopcock. Also in the upstairs airing cupboard I can feel the water pumping through one of the pipes (think it's a cold water mains pipe but not sure).

I have a combi boiler so nothing going on with a loft tank. Tried turing the boiler off just in case it was related (it's not) and have also bled radiators (there was a fair bit of air in the system).

The only thing that stops this intermittent issue is turning the stopcock off again.

Any ideas? thanks in advance!

 

[Scott_D]

Toilet filling
It may be overflowing internally

 

[Adam Jenkins]

Hi - thanks but it's not any of the toilets, I checked them. As I say the sound is coming from near the stopcock - the toilets are silent and are not running (well one of them does run a bit sometimes but that's just the inner plug not always sealing properly after a flush - just flushing again solves it) and they are not overfilling...

 

[Jim Goodenough]

I have a combi boiler so nothing going on with a loft tank.

Are you sure you have a sealed system, very rare but it could be the ball-valve opening on F&E tank if it's an open vented system?

 

[jtsplumbing]

Pin hole in plate heat exchanger.

 

[Adam Jenkins]

Found the problem and it WAS one of the toilets running that was to blame (sorry Scott_d)!!

The plug is leaking just a little bit and the water level is only dropping a tiny amount which is why I didn't notice it.

Thanks a lot for the advice!