On Fri, 14 Nov 2008 23:13:01 +0000, Steve wrote:

I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in the
kitchen will eventually replace the old back boiler, but for the time
being I want to run the new pipework with the old boiler/pump.



The old system had a total of about 4m of 22mm pipe with 8mm pipes T-eed
off and some 8mm manifolds.

This sounds very, very unlike a one-pipe system. Are you saying it was
like this (ASCII art pre)

--------
| |
| |===== . . . . . . .
| | . (rest of system omitted)
| boiler | 22mm .
| |=====+=+==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

rather than this:


--------
| |
| |=======+==. . . . .
| | | . (rest of system omitted)
| boiler | | 22mm .
| |=====+=|==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

??


Suggestions on how to diagnose/fix this will be gratefully received.

Need to be clear on exactly what it is to start with.



--
YAPH http://yaph.co.uk

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh