Water flowing into cold water tank from hot water cylinder

[rustyands]

Evening all!

I have a problem! I have water flowing from my hot water cylinder via the cold feed into the cold water tank in the loft. The system is a vented system.

It does this when all power to the boiler is removed, just slowly filling the cold water tank up, until it overflows.

Any suggestions please?

Thanks

 

[Winston]

Its likely to be the immersion at a to higher temp.

 

[stevetheplumber]

mixer tap or thermostatic mixer with a mains cold feed crossing over can cause this have you recently changed any taps ?

 

[Puddle]

Persume ball valve not leaking
If Ok as steve says also could be a pin hole in the coil of the cylinder and if heating tank higher than main tank, could leak through to main tank causing over flow
To check isolate header tank and see if level falls

 

[STEVEDIY]

have a similar problem

 

[STEVEDIY]

i have got water entering cold water tank not via the pipe to the ballcock
have recently fitted a mixer basin tap as well as a shower mixer, is one of these faulty or have i done something wrong. both mixers are mains cold water

 

[BLOD]

Sounds like you know the where the problem is already.
Isolate the supplies to the shower and mixer one at a time to see which one is passing.

 

[STEVEDIY]

i assume from that if one is passing there is a fault with it and could I fix it by putting in a one way valve

 

[Whyme]

A non return valve on the hot pipes. as original post cold pushes up the hot and into the tank cos there different pressures. Nowt wrong with the kit youve fit its the fact you havent fit any nrv's. Unless the mixer is specifically for low cold pressure which i doubt.

 

[STEVEDIY]

just to be sure, can I use a single nrv before the hot pipe splits to the basin and shower mixers

 

[PlumbBobBob]

ascertain which is passing first before fitting a nrv. double would be better also.

 

[STEVEDIY]

one last question, on looking for nrv there seem to be single and double options, what should I use in this instance

Thanks
Steve

 

[STEVEDIY]

sorry just reread your last post and now understand your reference to double would be best

thanks for everyone's help