When central heating is on the overflow pipe leaks outside?

[rob777]

Hi all,
When the central heating is on the overflow pipe leaks outside from the loft?
When it's off it doesn't.
Any theories chaps?
I'll get up there later if anymore info would be useful?
Thanks
Rob

 

[weareleeds]

With no info i could only guess that you have a combi & the exp vessel needs pumping up with air

 

[rob777]

I have a gravity fed storage cylinder

 

[weareleeds]

In that case switch on htg & check if water is being discharged into f&e tank if so you have a serious problem as system may be blocked

 

[GasMan1965]

There are loads of reasons this can happen inc blockage,, It can happen also when the coil is going in the cylinder !!

 

[rob777]

Thanks chaps, I'll investigate some more.

 

[gigz]

Should only be a couple of inches of water in the tank, turn supply off then take a few jugs of water out (or use drain off), bend ball valve arm down, turn supply back on and make sure water stops, it could be washer or split coil.