boiler pressure is rising to much on central heating side and water leaking from vent pipe

david drury, March 2010

The Domestic Hot Water ( DHW ) heat exchanger is fractured, allowing mains pressure cold water, normally contained inside the heat exchanger, to continuously leak out into the Central Heating pipework which surrounds it, thereby increasing the system pressure. The pressure relief valve is working as it should, by allowing the resulting dangerous rise in system pressure to be drained off to the outside of the house. Fit a new DHW heat exchanger. ( a simple job )

Frank, March 2010

Either

Pressure Vessel needs Re-charging- Open Pressure relief valve (drain system), find valve on expansion vessel and pump up to 1bar (if alot of water comes out of this valve, vessel is faulty and will need a new one) Then refill sytem

or...

Braided hose to the Vessel is blocked. Needs unblocking (Be careful as the blockage could be holding alot of water!)

Paul, March 2010