"David Hansen" wrote in message
...
On Sun, 5 Mar 2006 13:58:44 -0000 someone who may be "Doctor Drivel"
wrote this:-

That is why on combined feed &
expansion pipes it has to be 22mm minimum.

Here you appear to be mixing up two pipes.

Nope. A combined feed and expansion pipe is one pipe. Legal on systems
which sealed system compatible boilers may be fitted. And no need to have a
blow-off valve either.

The one pipe has system water move up and down the pipe,

The name feed and expansion pipe is something of a clue.

Yes it is. I have the clue and also explained. You should understand what
it is.