Does such a plumbing part exist?

Why not remove the WM tap from the pipe, add a short length of pipe with a tee piece, refit the tap to the end of the extended pipe and take the feed to the outside tap off the tee.

Sometimes I feel so dumb. :-) Thanks for that advice.

It is a compression fitting on there at the moment with very little exposed

In message , Periproct writes

Just undo the compression fitting and replace with a compression T-piece leaving the nut and olive in place

Take 5 minutes out just to think it through properly

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Periproct" saying something like:

Or re-use the existing olive and nut, just wrap some ptfe tape around the olive. I only suggest this to avoid stressing a stub of pipe, but it should work perfectly well, with one proviso - the protruding stub of copper after the olive should be short enough to allow the olive/ptfe to seat and seal properly into the leg of the new T. Sometimes older fittings are quite deep and the protruding copper is too long, needing a trim with a junior hacksaw.

Sounds a bit drastic. Normally catheters have much smaller taps fitted.

:-) I think at her age my Mum might appreciate having a tap fitted.

Boss white - much better.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember 1501 saying something like:

Oh yes, no problem on new fits. I tend to use the tape if it's an old olive being re-used.

Note that the sealing surfaces of a compression fitting should have absolutely nothing on them. I sometimes use one turn of PTFE as a lubricant on the thread, but being careful to keep it out of the sealing surfaces. (Never use anything on a gas compression fitting, because it's impossible to prove you haven't got in on the sealing surfaces.)

If the sealing surface has been damaged (e.g. by a sealant having been applied in the past), and it's not replaceable, then you may have to continue using a sealant for ever more.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) saying something like:

No skin off my nose. I do what I've found works, and damn the theory.

You've made a home-made compression-washer joint. It's a joint, not a bad sort either, but it's not a metal-to-metal compression joint any more.

Personally I wouldn't do this. Not because switching away from metal- to-metal is so bad (it's only domestic plumbing, so pressures, temperatures and hazards are low) but because PTFE has cold flow behaviour under strain. Compared to elastomers, it's a poor choice of sealing washer. It works for threads because the surface is wide and the gap is thin. It's much less good over olives because the sealing area is narrower and mostly thicker. It'll seal, but it won't last as long as a metal-metal joint.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Andy Dingley saying something like:

Thousands of joints, no leaks. Thanks for the lecture, anyway.