it is more than likely to be ur diverter valve which diverts ur hot water to ur central heating this may need to be replaced
jm, April 2009
it's the diaphragm inside the diverter valve that has failed. you don't need a full diverter valve (these are about £90) you can get the diaphragm on it's own for about a tenner
andy gas man, April 2009
Domestic hot water diaphragm has probably failed
andy gas man, April 2009
Your boiler has a diverter valve inside, that directs the hot water either to the taps or the radiators, and I guess it has packed in.
