I have a newish boiler (gas) which has at the top a brass gizmo that (is supposed to?) release air trapped within the system. I think it's duff...but just below it is a little tap which, it I open it and have a bucket handy spurts out hot water + air. The boiler 'gurgles' along, so I'm guessing I have air in the circulating system. I've bought one of the litle grass canisters, which has a plastic screw on top piece and inder that it's like a bycycle tyre inflator on the tube.
I'm in France and have tried to make sense of the plumber but it's become 'complicated'! He's a long way away and simply can't get here. I assume I have to drain the system before unscrewing the old device and popping on the new one? It's called a 'purgeur' which makes sense since it purges the system of air!

But any help/advise would be appreciated.

Thanks.

Ken Tickle, November 2008

oh and dont forget to open new air vent up slightly :-)

iain, November 2008

if its a auto air vent on a combi boiler you should be able to get away with just dropping the pressure to zero rather than fully draining or isolating. If its just gonna be one open end while you swap auto air vent just drain from boiler or a rad until combi pressure goes to zero. Nip up rad or boiler drain depending on what you used and remove and replace vent. nip up and re-pressure to 1.5bar

iain, November 2008