On 22/02/2017 12:33, GMM wrote:
I know this is an outrage and I should be hung drawn and quartered for
even contemplating it but needs must (!)

I have an old 6-foot single radiator in the bathroom which is beyond the
end of its life and showing (since yesterday) a small rust hole/leak. I
have a 1m double that would do the job in its place. I'm planning to
renovate the room comprehensively later this year but currently have
very little time available to do any major surgery on the CH system.

What I would like to do is join some copper or plastic pipe to the old
valves then mount the new radiator to this. This will save me draining
it all down, lifting the floor and re-routing the pipework for the
moment. It will also, of course, look dreadful but it's a temporary
measure so I'm not worried about that.

I know you can get extending tails, but they wouldn't stretch this far,
so the question is, what do parts I need to join the 'radiator' side of
a valve (TRV and LS) to 15mm copper tube? I'm imagining it will be
something like a 3/4 tap connector but I'd rather make sure I have the
right thing before I get up to my eyeballs in the job!

Normally I would just go and chat with my local PM but I went round
there this morning and to my horror they have closed down, so I need to
go and cultivate a new one somewhere.....

Cheers chaps

As others have said, it may be easier to put a temporary patch on the
rust hole.

But, if you really want to do what you suggest, it is perfectly feasible
but the fittings you need will depend on what type of tails your current
valves have.

All tails have 1/2" male BSP threads at one end, which screw into the
radiator. Older valves have conical connections between valve and tail -
and these come in two different sizes and several different threads!

Newer valves have 15mm compression fittings - both for the tail and for
the supply pipe. This enables such valves to be used in either orientation.

I'll deal with the compression type first, because these are easy. All
you need is a length of 15mm copper pipe and a 15mm straight compression
coupler each side. Remove the tails from the old rad and fit them to the
new one, leaving the olives and nuts in place. Use the couplers to
attach a length of pipe to each side of the new rad - making use of the
olives and nut already on the tails, thus leaving a spare olive and nut
each side. Cut the pipes to length to marry up with the valves, and use
the spare olives and nuts to attach them to the valves.

If you have the conical fittings, it's best to keep the tails with the
valves. So you'll need two new plain tails, two couplers and two 1/2"
female iron to 15mm compression fittings. Remove the tails from the old
rad and re-attach them to their valves. Screw a 1/2" female iron to 15mm
compression fitting onto each tail. Fit the new plain tails to the new
rads and fit a compression coupler onto each tail. You then just need to
fit a length of 15mm pipe between each pair of compression fittings.

You will, of course, need to use PTFE tape on the tail threads before
screwing them into the rads and, if appropriate, on the tail to female
iron connections.
--
Cheers,
Roger
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