How to Drain a Ariston Mircogenius II 27 Boiler?

Unfamilier with this boiler, however, this drain-off-c*ck sounds right. You'd be better off draining down from a d.o.c. on a radiator - just check all the tails on the rads and you should find one there (occasionally the d.o.c.'s can be outside, flow and return). If you drain down from a rad, all the water should drain off, however, from a boiler which is higher than some rads, this would not be achieved.

Is it a sealed system (with pressure gauge etc) or open vented (with a header tank)?

Angus

Hi it's a sealed system i've looked at all the downstairs rads and none have this vaule like the one on the boiler.