Water coming out of the overflow pipe

[InNoX]

Hi,

really hopping someone can help.

first of all i have an vented system with an f&e tank for the heating and cwsc for the water.

when the hot water is turned on i get water coming out the overflow pipe for the cwsc.
things that i have tried are;

i've turn the thermostat down on the cylinder and it turns the boiler off. so guessing thats working.

the ball valve in the cwsc isnt leaking.

 

[muggles]

Which tank is overflowing?

 

[InNoX]

Which tank is overflowing?

Hi, the water is coming from the cwsc. not the f&e.

thanks

 

[InNoX]

its coming out of the one connected to the hotwater cylinder.

the heating has its on vent pipe that goes to the smaller f&E tank.