Hi, We have a Vaillant ecotec plus 831 boiler, it worked fine for about a year, we are now getting F22 fault code, the boiler constantly loses pressure and we have to open the two valves underneath to re-pressurize the system, we are doing this now on a daily basis, we had Vaillant out who told us there is a leak somewhere in the system and no problem with the boiler, it has been happening since January, 3 months! Surely if we had a leak we would be aware of smell or mustiness somewhere in the house, we have absolutely no signs at all, the house seems to be watertight, we then got the LDS Leak Detection System people in and they could not find any leaks, they were here for two days! We are very confused as to why an expensive branded product like Vaillant should be causing us so many problems, we have had another two plumbers out one to service it and another to put some leak stop stuff into the system, neither of these made any difference whatsoever, please help if you can with a possible solution to this conundrum! Thanks..