Not a big job at all. It will only take 15 mins if its a side flue or vertical flue. If Its a rear flue it can take up to 45 mins. The job can get a little messy with water escaping from the inlet of the vessel when removing.
gas man, August 2009
not that bad, but easier and probably cheaper to fit an external vessel if you have the space to fit one in. they're usually about the size of a football.
