Right now this is a bit of rhetorical question, but...
...how do you stop compression fittings from leaking? I plumbed in some new stuff at the weekend, but lots of the joints are now leaking. I resisted using PTFE tape on every single joint, but is that the answer? PTFE wrapped around every olive..?
G.
Don'k know about anyone else, but when I've done it the tape goes on the thread - not on the olive. Need to make sure that the pipe is smooth and cleanly cut and that the pipe stays well inside the joint through tightening so that the olive can be properly compressed onto it.
The message from snipped-for-privacy@eng.cam.ac.uk (G.W. Walker) contains these words:
The seal is made by the metal to metal contact between the olive and the pipe, and the olive and the tapered seat in the fitting. Both mating areas have to be very clean and smooth, the pipe has to be lined up well enough and the fitting has to be done up tight. PTFE tape can serve no purpose in a compression fitting whatsoever apart from to confuse the issue and make a balls up.
Why did you 'resist' using PTFE? Would you resist using a blowtorch if you were using solder joints? This is what PTFE is for, very rarely can a watertight seal be achieved without it....they just don't tighten up properly.
What bollocks, I've never had to use PTFE tape on a compression joint to seal it
Bollocks!!
very rarely can a watertight seal be achieved without it....they just don't tighten up properly.
A compression fitting is DESIGNED to give a watertight (and gas tight - with the correct fiiting) with only itself and the olive. PTFE tape is not a '"must include" extra for every fitting. If done correctly a compression fitting WILL be leak free without PTFE.
HTH
John
PTFE is not made for use on compression fittings. It never has been and never will be.
However, as with most diy offerings a resourceful person will read that it can be "used" on compression fittings but it is primarily geared(IMHO) for making a watertight seal on a thread/nut combination i.e where water can squeeze around the threads due to the space between nut and thread - otherwise you wouldn't be able to screw the nut on!!! The watertight seal in a compression fitting is made by the olive (brass ring) compressing slightly onto the pipe whilst at the same time being squeezed up tightly into the neck of the fitting. The subsequent mating of surfaces is watertight. Just try to pull an olive off a brass pipe once a joint has been 'done up' properly. In most cases you have to cut the pipe again.
My old man made them for 30 years and before speedfit/pushfit plumbing came along they were the godsend for DIY plumbers who didn't want to solder fittings. Yes they are a bit more wieldy and do take a bit more time but they give you the opportunity to break the joints and remake where a solder joint is usually well fixed for life!
Compression fittings do leak - ONLY WHEN you haven't followed the correct procedures or you have a faulty olive or fitting.
Some of the more common issues -
Don't reuse olives - they cost a few pence and if you have already squeezed them onto one pipe whilst doing up a joint, chances are the next pipe you stick it onto will be a slightly different shape.
Make sure the copper pipe enters the fitting in a straight line. If it goes in squint then you will have to tighten the fitting more and more until you get to waterfastness. If you tighten it too much you will start to compress the pipe and leaks will develop. A good rule is to get it to a tightness that feels comfortable ( 10 inch spanner ) then roughly three quarter turn from then. If you get leaks, then notch it up a quarter turn each time until the leak stops.
Make sure no swarf ( little bits of brass from cutting the pipe) get into the joint, either under the olive, or into the compression fitting itself i.e clean the pipe before you make the joint.
Don't use pipes covered in paint or other crap as they will affect the waterfastness. Either sandpaper off the paint etc where the joint is to be made or use a new piece of copper.
If you use plastic pipes then make sure you use a small pipe insert at the compression fitting. Yes you can make the joint watertight without it but given you are compressing plastic pipe then it doesn't take much to screw it up. The internal inserts costs a few pence and give the pipe some rigidity at the olive point.
Simplest way is to make all your joints as tight as you thing they should be( and you can make them reasonably tight) then turn on the water...Dry all joints with some tissue paper and wait a couple of minutes..Then go back over with a tissue and see if it gets wet. If no visible drips but paper is a little wet then that joint needs a tweak...If you have water p*ssing out of the joint then you've either not made it tight enough or you are missing an olive!! Yes it has happened now and again....
Good luck...
I have to agree with him Phillip PTFE was primarily a temporary fix solution in the early days of it appearing on the market until a satisfactory job was known to be good.
As the man said... "If done correctly a compression fitting WILL be leak free without PTFE".
As everyone else said, PTFE is a bodge.
It's supposed to be a metal-metal joint with the olive deforming to make a seal. Metal-metal seals are superior to almost anything else in their league if done correctly.
Common mistakes:
a) not preparing the parts - swarf etc;
b) Over tightening. Do the nut finger tight, then about one turn with a spanner. It's better to err of being undertight, because you can tighten more. Over-tight and the olive is bent. Turn the water on and look for weeping joints, tighten gently until they don't. Eventutally you get a knack of how tight to do them in the first place.
If you do get a weepy joint or if you are having trouble with re-assembling an old joint, a slight smear of Boss Green on the olive should fix it and is less of a nasty hack than PTFE.
Cheers
Tim
I agree - gritty dirty parts are the enemy.
John
You may not have tightened them enough, undo one and look at the olive. It should have squeezed into the pipe by a small amount, enough so that it's tight on the tube but not excessively sunk into it, or deformed. If you have not done them up enough, do them up a little more until they don't leak! If you've over-tightened them, they're scrap.
You should not use PTFE tape or anything else on these joints.
Either you've not tightened them properly, you've had a poor quality batch (unlikely), or your preparation was poor.
The pipe must be undamaged and cut square with a proper cutter. Then cleaned till it gleams with either wire wool or a suitable abrasive material.
Examine the mating surfaces of the olive and fitting for signs of damage or swarf etc. And it should be spotlessly clean - same as the pipe.
If all this proves OK a properly tightened compression fitting won't leak.
Fernox LX is a better bet these days.
Ta for all the replies. I couldn't see how PTFE would help either. The pipes are new, spotlessly clean, cut absolutely square, and the joints aligned well.
I'd not appreciated that it was possible to over-tighten them -- looks like that might be where I've gone wrong with some of them. Time to dis-assemble and try being less enthusiastic with the spanner this time!
Thanks again.
G.
The message from "Phil L" contains these words:
PTFE tape is for joints which use the thread to seal - which compression joints don't.
IMHO it's near impossible to overtighten them with normal spanners - although you obviously could with large Stilsons etc.
With a properly made compression joint it isn't possible to remove the olive without splitting it - it should be sort of cold welded on, without noticeably distorting the pipe diameter.
If you can pull off the olive or turn it it wasn't tight enough.
Olives are always well compressed on to the pipe when I've dis-assmbled joints in the past. Never seen a loose one.
Serves me right for not soldering them all I guess!
G.
Nothing's "welded", the olive indents the tube a fraction. It doesn't need much.
That's why I said 'sort of' meaning it can't be moved.
Even when visibly defect free and cleaned with fine wire wool some compression joint components will leak. They usually don't but it does happen. So, I have 2 different approaches to these joints.
Sometimes the joint is going to be in a location where it's not possible to put it to the test until a floorboard or other type of covering has been put in place so that the rest of the job can be assembled. These joints I always smear with Boss or wrap the positioned olive with a couple of turns of PTFE tape. It's a sin but I like it.:) I then do the standard finger tight 3/4 turn with a spanner, plus a big pinch for luck. Where possible with these hidden before being tested joints I leave the loosely draped end of a long strip of cotton fabric like a strip of old T-shirt around the joint and trail the other end out of the confined area to a handy spot where, after turning the water back on and giving it a little time, I can pull the strip of fabric out and check it for dryness.
Most other compression joints that are visible and accessible I usually leave tape or paste free and err slightly on the side of slackness when tightening the joint. Then when the water's turned on any that are weeping can be given an anti-depressent tweak.
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