Water flowing back up cold feed from water tank.

[MrSmoith]

I have a Sealed system (vented DHW) and 2 days ago the overflow in the water tank in the loaf started gushing out water. It then stopped one evening but has since started up again and continued gush water none stop.
We had a problem like this last year and it seemed to right its self but it did not go on for this long.

It still gushes water weather the hot water is switched on or not and the heating system is off.

I took the lid off the storage tank in the loaf and found it was filling up without getting water from the cold in or the expansion pipe. So I put my fingers over the cold out and could feel a strong pressure of water coming back through the outlet.

When I blocked this flow with my fingers, water would then start to come out of the expansion pipe.

Would appropriate any information on what might be wrong or how i could temporary stop the leaking water, in till the problem is fixed.

 

[breadnbutter]

are u losing pressure on the sealed heating system,or is it connected to a pressure reducing valve and open, . it possible your hot water cylinder coil is holed.

 

[Riddor]

I would be looking at either a mixer tap in the kitchen - or if all your cold taps are mains water fed then could be a shower mixer cartridge letting by. test by closing off the isolation valve to the tap would be the first step.

 

[MrSmoith]

Yes there is a slow pressure loss on the sealed heating system.
No we don't have a pressure reducing valve.

The kitchen taps are mains fed. I do have a shower mixer cartridge but the builders never made an access panel to get at the stop valve. The shower head its self is not leaking, is there another way I can test if it is this?

 

[Riddor]

unless its mains fed cold on the shower, it wont be that. its going to be where the mains mixes with hot so to speak, mixer tap, or coil gone in the cylinder as pointed out by breadnbutter.

washing machine cold feed only?

how often do you top up the heating system?

try and isolate the kitchen tap - either the hot or cold. that will eliminate that as the problem.

edit - just turn off your main stopcock to prove or disprove it has something to do with your taps/mixers and take it from there

 

[Riddor]

to check if the coil in the cylinder has gone - drop the pressure in the boiler down to naff all and then check to see if it stops flowing up the cold outlet in the tank in the loft. if when your re pressurise it up and it starts again, then that seems to be the issue

 

[MrSmoith]

I found a cold water stop valve that was supply the extension which is where the shower is. Since I turned that off the leaking has stopped.

Guessing that is the problem and I need to replace it. Thanks for all advice.