L
london
hi can anyone give me some advice . my vitodens 100 boiler keeps dropping water pressure . every 5 days it drops tp .5 bar and stops working . i have looked for any signs of leakage at the radiators but they look dry , i have had the boiler for 6 years and i can remember the viessman engineer comming outfor the same problem when the boiler was 6 months old and he replaced the expansion tank . then when under warrenty with british gas the same thing and he re pressurised the tank , is this a common problem what would you recommend ? cheers