Expansion tank leak

[2Colin]

Hi, wonder if i can get any advice with my central heating issue?
My expansion tank overflows very slightly, (dripping) while the heating is on. I have checked the stop cock which is ok and re-adjuster the water level to a lower position but the water level has crept back up by about an inch causing the level to pass through the overflow outlet? any suggestions or is this normal? i have a condensing boiler feeding 9 radiators.

 

[Agile]

Is the float valve leaking?

Did you set the level to about 100 mm cold???

Does the warning outlet allow 200 mm increase in level?

Those things first!

Others may follow!

Tony

 

[2Colin]

Hi Tony, thanks for taking the time to answer my query?

The float valve is not leaking as the overflow only drips after the heating has been on a while and not when the heating is off.

Regarding the next two questions i think you have given me the answer as the expansion tank outlet is 200 mm from the base? The level is about 100 mm cold.
The tank measures 280 mm WD x 430 mm LG x only 300 mm Tall?
I have a feeling that the tank is not big enough to allow for the expansion on the system as i am only left with 100mm for expansion? Would you agree and do you know what size roughly the expansion tank should be?
Regards, Colin.