Over flowing header tank

[Fallout]

Whats the best way of telling if this is a pin holed coil or fill valve not shutting off. Thanks. Imagine just check if the fill valve is shutting off.

 

[Nige F]

that's correct

 

[Fallout]

Thanks it's been doing it a while slowly. If was a pin holed coiled. Do these usually get worse over time or stay consistent? Thanks

 

[dilalio]

Isolate supply to fill valve.
If it doesn't have one, put one in.

 

[oldbuffer]

Three possible reasons for central heating header tank overflowing:
1. Fill valve not shutting off. Per. dilalio above.
2. Central heating pumping over. Could be various causes, including blocked system feed, pump on wrong setting. Tie an empty jar under the vent and see if it gets water in it when heating comes on / goes off.
3. Pin holed heating coil in hot water cylinder and central heating header tank lower than cold water storage cistern.