HI just for a change no low pressure but my vokera boiler which was fine during winter since turning it to hot water only for summer is now pressurising the system goes form 1.5 bar to 4 bar in 10 days or so so bleed rads to let pressure back down and it goes up again ac ch is off and filling loop is in normal position I guess there must be a leak in perhaps the heat exchanger???? or am i totally wrong trying to think where cold supply connects when heating is off plz help ta