"geoff" wrote in message
...
In message , Nigel Percy
writes
Hi,

Right all you knowledgeable persons. I moved house and am trying to get
to
know
the various bits & pieces. What is the arrowed component in the following
picture

http://www.btinternet.com/~nigel.percy/heating.jpg

Looks like an automatic bleed valve to me - it has a float chamber
inside
--
geoff

How effective are these ? I've got one fitted but a small amount of air
still manages to collect in the bathroom radiator every couple of months
during winter.