if your just working on boiler there are three black handle isolation valves under boiler. turn them off, open hot tap to drain water side and to drain system side, remove white front panel, drop electric tray down and look into bottom right corner. there is a drain off with white wheel type handle. connect small hose to drain off and turn white wheel.
Note: as air enters through fittings you undo, you'll get more water and even bigger note!!!!!!!!
snap the isolation valves and you have bigger fish to fry!!!!
iain, August 2008
