Brass coned compression fit woes.

[trees]

I've tapped into my hot and cold supplies to feed a vanity sink in the dowstairs loo, as per wife's instructions.[;-)]

The supply pipes were 16mm, and I wanted to run 12mm pipes to the taps, so I bought coned compression fit adaptors. I didn't solder, as it was too difficult to get at.

After using copious quantities of PTFE tape, I've got the cold connector to seal. It took three goes[:(]

When I left the house in October, the hot connecor was still weeping from one of the reducers. It didn't matter, since the hot water is off anyway, and drained.

When I go back this weekend, I'll have to seal it.

So, to my point: should I strip it and put even MORE PTFE tape in? Or should I strip ALL the PTFE tape out, flux it, and run solder copiously into all the joins except those for the compression fittings, of course?

I have a gas torch that will easily heat it, and can take English water-based flux with me, and soft lead-free solder.

Once I'd soldered it up, I would allow it to cool, wash it to remove all flux and refit it.

Any advice, anyone?

Thanks.

[Nick Trollope]

PTFE is for use on "broken" thread fittings. Most in France aren't, so use hemp/paste.

Don't quite understand your soldering idea, although I wouldn't. If you have decent quality compression fittings, then they will work.

[Le Plombier]

You should not need ptfe for a compression fitting joint

Likely issues

They are cheap fittings with plastic cones, change the cones for brass

The pipe is not round in section

You have not inserted the tube correctly

There is dirt or grit in the joint

A correctly assembled compression joint should be water tight with only a quarter turn with a spanner past hand tight

If you solder the fitting as you describe you will never get a leak tight joint, you will probably make it worse

Le Plombier

[BIG MAC]

Begging to differ, PTFE Tape is an ideal way of creating a seal without over tightening a joint wound around a brass (Hard) olive, I wouldn't bother with cheap copper or plastic? olives quite how you would get plastic to bite the tube thats it's being compressed onto is interesting right enough. PTFE  tape allows to take up minor deviations between olive and seat and helps prevent the uninitiated overdoing things (what it actually does is form a ring of more plastic material between olive and seat). Water Hawk, Bos white or similar used in conjunction with hemp is ideal for tapered threads don't use it in conjunction with PTFE tape though!. Soft soldering a compression joint is an excercise in futility Le plombier is quite right. More as likely if you have seated the compression ring (Olive) correctly you will simply need to isolate, drain down and wind off the back nuts pull back the tube slightly to permit an application of pipe jointing compound ie. water hawk (Suitable for potable systems) then make up the joint again supporting the joint body with grips if needs be to allow the back nut to be tightened correctly.  Tres facile

 

[Gluestick]

When I first "Met" PTFE tape it was love at first sight!

At the time, I was installing a new airline in my garage workshops: 300 odd feet of handthreaded 3/4" galvanised water barrel, BSP taper, of course.

Prior to the wonders of PTFE it was all Boss White and Hemp: a messy old job it was too.

People seem to believe PTFE is a sort of bodge it solution for leaks: anymore than Red Hermatite is a solution for a muggered up gasket: it isn't. The plastic tape melts under pressure and heat (which is why it was also used for high speed electric motor bearings), caused by the fiction and fit of opposing screwthreads; it is really the squashing and "Wiping" pressure exerted between the peak of the thread form and the trough sides, popularly called the "Nip".

A good compression joint uses the screwthread to tighten the olive on the opposing face: and simultaneously tighten the olive on the pipe.

If all the components are correctly shaped, then no jointing compound should be needed.

We all tend to use jointing compound simply to take up any tiny irregularities in the faces.

I have used PTFE to "make" joints for gas up to 3,000 PSI as well as hydraulics systems working at significantly higher pressures.

It is no effective substitute, though, for an ill-fitting joint. Or an oval pipe or one with indents and deep scores. The olive simply won't seal.

[Chancer]

[quote user="Gluestick"]

At the time, I was installing a new airline in my garage workshops: 300 odd feet of handthreaded 3/4" galvanised water barrel, BSP taper, of course.

[/quote]

I used electrical conduit as it was a lot cheaper, at the time maybe 10 years ago I was paying £2.05 + Vat for 4 metres (why do I remember irrelevancies yet not what I did yesterday?), it hasnt ruptured yet but was a bugger to seal as all threads were parrallel, one joint still leaks.

[Gluestick]

All I remember, JR was trying to install the new airline around a very busy workshop, between working myself and sweating to thread each bit of pipe with an old pipe vice and a mansized pipe die; and then wind on the T junctions and drains and downdrops and the right B****r it was going around obstacles: and capping each progressive end off so it could be used, pro tem as it grew!

And all this after I'd built the new compressor: and my ex partner and I had laboured night and day to install totally new wiring so the lads couldn't move more than two feet and fall over a double-13 metalclad outlet.

Surely, conduit was thin wall and rolled with a joint?

It ought to have burst apart! [6]

[Michael]

Trees. It sounds like you are putting the Ptfe tape around the thread of the fitting which is incorrect.Three turns of tape around the olive on the pipe will solve the problem.Michael.