i have pumped heating and gravity hot water , just lately when the boiler switches off i get what sounds like boiling water spurting out of the over flow pipe into the header tank any ideas ??????
Could be a Boiler Contol Thermostat Fault, is the Hot water hotter than normal?, other causes lack of water in system, is the Ball Valve in the Header Tank Stuck?
Worst case - Heat Exchanger could be blocked due to age & Sludge etc