I am a post qualified level 2 no nothing plumbing student or know very little anyway!!! I was asked at work today why this guys combi boiler was regularly showing high pressure on his gauge. I do not know anything about combi's, but he did say he has to regularly bleed his rads. The boiler is only a couple of years old and the rads not much older. Is the system drawing in air from somewhere or what. Said I would try and find out. Thanks.