sorry i aint a plummer but my radiators all have a little plug at the top on the end and if you look in the middle it should have a little square that the key fits onto, you turn it a few times till you hear the air hissing out (but watch out for the water as it can be muckyand can dirty walls and curtains)then close it as water starts to come out, do the same to all radiators and bobs your uncle
p bainbridge
October 2006