While filling the loft in my new house with all the rubbish you never need but (she!) can't bear to throw away, I noticed that the Central Heating header tank contains steaming hot water (causing lots of condensation on the underside of the roofing felt)! It seems that when the pump is running, even if I run it at minimum speed and both hot water & radiator control valves open, the pump if forcing hot water up the Vent pipe in to the header tank??? The pump is mounted horizontally with the Vent & feed conneting to it via a horizintal feed from the boiler.
What are the recomendation for Vent/feed/pump postioning and head? As I don't know the history of the systen it's possible this is an installation fault? Advice greatly appreciated.
Bert