How can i fix my Ariston Combi Boiler?

hi geoff the problem you have is with the diverter valve it will either be internally coated with sludge from the heating system resulting in the radiators getting warm when you are using hot water only or the water valve diaphragm has sptit . the water leaving the overflow will be due to a worn safety valve or too much pressure being put into the boiler by you via the filling valva assy or the boilers expansion vessel has lost its charge pressure resulting in the boilers internal pressure rising to above 3 bar gauge pressure after the boiler has been on for approx half an hour. the boilers safety valve is set to release water to outside at approx 3 bar and is preset by the manufacturers hope this helps

joe waldron
April 2005