"Phil Addison" wrote in message
...
On Wed, 7 May 2003 23:35:11 +0100, "John Stumbles"
] wrote:

"Chris Hodges" wrote in message
...

I've got a cold cistern (in the loft) which just feeds the bath
cold
tap
and the inlet into the hot cylinder. After going up to put some
fernox
in the F+E tank I noticed that the expansion pipes for both the
loop
(i.e. boiler, rads + heat exchanger in cylinder) and hot water
(taps)
discharge into the cistern.
...
How much of a big deal is this? There's no easy way to tell which
pipe
is which to divert one into the F+E (which doesn't have much value
in
terms of expansion).

you should be able to connect mains from the feed to the ballcock to the
vent whle you're replacing the ballcock: if you've got some compression
fittings, pushfit fittings and garden hose handy (and you can't be
serious
about plumbing if you haven't :-) you should be able to hook something
up.

An easier way is the reverse! Bung up the pipes and see which one STOPS
the water flow out of the hot tap. Get a pair of Drayton bungs - they
are conical and will fit into 15 and 22mm tube (but not 28mm). Put one
in the exit pipe of the domestic hot water header tank - that will be
under water at the bottom - and the other in one of the vent pipes. Then
turn on a hot tap in the bathroom. If you have the correct one no
virtually water will flow. If you have the 'wrong' one, the contents of
the pipework from the tap up to the open vent will flow out, just a few
pints.

If the bathroom is downstairs, leaving the hot tap on with the pipes blocked
will result in the collapse of the domestic hot water tank - a frequent
occurrence in winter where the two pipes are frozen. Depending on the height
of the tank you may have a problem with an upstairs bathroom. You may be OK
if the tank is very old (they were a lot thicker then). A rather risky
technique! If you must use it, as soon as the water slows (ie you notice an
effect) shut of the tap and remove the bungs (or one at least).


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)