why does the domestic hot water keep leaking into the radiators?

d you are absolutely correct.....just read the post again and somehow I had thought that the pressure rising inside the boiler. (blush)

John
November 2009

the other guy is wrong if you have a combi boiler then it will be your diverter valve. If you have a sealed system with external valves then there will be a 3 ways valve or two 2-way valves and there will be an issue with the htg valve, or in the example of the 3way valve the hot water will be passing around the htg side of the 3 way valve.

d
November 2009

Your boiler needs a new DHW heat exchanger - as one is leaking into the other.

John
November 2009