Ed Sirett wrote:
On Wed, 23 Mar 2005 10:43:25 +0000, John Orrett wrote:


Set Square wrote:

In an earlier contribution to this discussion,
John Orrett wrote:



Thanks for the reply Ed; yes, we are in a 3 bed semi! So it
theoreticaly should be a case of drain the system, take old pump out,
fit reducers at either end, and then install new pump (presumably
having to cut off a bit of pipe either side to allow the reducers?).
I assume that reducers from 22mm to 12 mm (ish) are available?
Regards
John


I don't understand your problem! I don't know what sort of pump you saw with
12mm connections - but it was unlikely to be a central heating pump!

AFAIK, virtually all CH pumps have flange connections with a 1.5" BSP
thread. [See
http://www.screwfix.com/app/sfd/sea/...&cd=1&x=8&y=13
as an example].

You then have a valve similar to
http://www.screwfix.com/app/sfd/sea/...cd=1&x=10&y=10
on either side of the pump - which screws onto the threaded flange and
connects to the 22mm pipework.

You can normally close the valves to retain the water in the system, unscrew
the valves from the pump and insert a replacement pump - all without
draining down. The only provisos are (a) that the valves work and (b) that
the replacement pump is the same physical size in respect of distance
between flanges.

Hi Set Square - I see where you are coming from!Thanks for the links,
that made things much clearer. I didn't realise that the pump valve gate
was a separate unit. I thought it was an integral part of the pump. So
presumably it should just be a case of close both valves, turn off the
electrics ,unscrew the pump from the pump valve gates and remove the
wiring, and then reinstall? I'll put a bit of WD40 on the valves in the
meantime. I'll check the distance between flanges also!
Thanks again,


That's the theory. I practice with kit that's been around for 25 years you
_will_ end up draining the system and fitting new couplings and pump.

The rubber washers between the pump and coupling flanges will have been
turned to charcoal over the time, but new ones come with the new pump.

HTH


I thought it sounded too easy! Maybe I'll ask our local central heating
merchant to come around and do it! I'm sure it probably needs inhibitor
in it anyway, so maybe it wouldn't be a bad ideaa draining down and
starting again. Our local neighbour reckons British Gas are charging
£450 for a powerflush!
Thanks again for the advice,
John