Keego i know my thermostat is working ok. I have turned the isolation valve off on the cold feed into the tank, but it still keeps rising substantially when i turn on the hot taps it lowers the level back to nornal in the cold storage tank. After abou two days its full again and the overflow...
I have noticed a leak from my overflow. Tracing it back it appears to be from the cold water storage tank in the loft. I checked the tank and it was nearly full to the top. I have checked the ball valve which is fine (no leak or drip). The expansion tank was probably only 1/3 full nowhere near...