Hi all I've had pressure problems with a glow worm 35ci now for a couple of months for some reason it works for a few weeks then starts dumping water out the prv had a chat with a plumber in the pub (ha ha yeh i know) and he reckons it the expansion vessel i have some plumbing know how and will do the job no problem all i need is a diagram or picture of what it looks like any help would be appreciated as the wife is really ****ed with the cold now.