Compression joints

Aug 03, 2004 27 Replies

generally yes. But you can undo a joint and re-tighten. When doing so smear some jointing paste over the olive.

The joint has been overtightened. You may need to cut it off. There are some olive extraction tools, which are expensive though.

The makers say you don't require compound. If everything is perfect they are correct. Experience has taught people to smear the olive in paste.

You can try wrapping the olive in PTFE tape, sometimes that works.

I've got some basic questions about compression joints in 15mm copper plumbing which I didn't see answered in the FAQ.


  1. Is it true that you should never re-use a compression joint without replacing the olive?


  1. Should you normally be able to remove the olive when dismantling the joint? In every case I've done it, the olive is embedded into the pipe and can't be removed.

  2. As far as I can tell, no sealing compound should ever be used on a compression joint. Is this correct? Dismantling joints made by our most recent plumber, they all seem to have a sticky green paste in them.


  1. If a compression joint has been re-assembled and is leaking, I assume the first step is to dismantle and make sure it's all clean. If that fails, and if cutting back the pipe and letting in some more to fit a new olive is not an option, is there any sealant I can try as a last resort?



Thanks in advance!


I have successfully removed an olive using some cheap pipe pliers, and then remade the joint with a new olive, with no problems.

Ben

...you get paid...so you are a an amateur...and it shows.

...this man is deluded. He will be saying he can tango dance better than me next.

Mobile phones should ne banned.

Ok, I'm afraid I'm going to have to ask to explain, just can't parse that one. Slowly, in simple words, WHAT DO YOU MEAN???

It means you haven't a clue, so stop giving poor advise.

Care to say why it is obvious that this doesn't work...as that is not my (limited) experience

I've recently had the toilet out about half a dozen times, due to completely refitting the bathroom, tiling, having some lino put down, getting them to take it back up again a they ripped it while installing, geting a new batch etc... and the whole point being that the connection to the cistern inlet is connected with a platic pipe and compresion join, and has perfomed excellently despite being re-made so many times.

After the first disconnection , I went down the PTFE around the olive route, and have fortunately had no probs with it.

cheers

David

Erm, ok. NOT!

Hey, tell you what, fancy meeting up at the uk.d-i-y Axminster show do? I bet a few regulars would come along just for the opportunity of meeting you!

Most definitely poor advise.

No.

That is understandable as my tango dancing is reputable. You should see me do the ch cha cha!

Personally, I never use sealant on compression joints. I'd rather the seal was done properly as intended, rather than using some gunk that will have rotted away within 20 years because someone is too scared to tighten the joint up properly.

I tighten it a bit more. If this doesn't work, I throw the entire lot away. The cost of an extra compression coupling is nothing compared to the cost of water damage from attempting to seal a damaged fitting with gunk.

Christian.

Let's taste it, after imbibing vast quantities of chlorine, fluoride and aluminium salts over the years, a wimpish set of toxins like those liable to be found in Fernox LS-X will just bounce harmlessly orf of one's atrophied organs and bio-plumbing.

I doubt very much if there is a cold weld, it's very difficult to make cold welds and the level of cleanliness and pressure involved in a compression fitting is such that it just wont happen.

I've done whole house CH systems with compression joints and had no problems at all after many years. If they really "leak on a very regular basis" no one would use them anywhere.

I quite agree that overtightening won't help though.

People buy cheap and nasty compression joints, don't know how to us them, have problems and them say this is the norm. Good quality fitting will last for decades. My moths house was fitted with compression joints and nothing went wrong after 50 years.

Where do you buy cheap and nasty ones? I've not noticed much difference in quality between any.

There's a hole in that statement.

I reckon cold weld is going a bit far here, by some distance.

Yeah I'd agree that plastic pipe will certainly deform and the olive will embed in it, but I'm not too familair with your internal fraturing of polymers explanation, nor crack propagation in plastics, but it is an interesting theory. Do you really mean fracturing of polymer, as in the polymer chain being broken?... would that not require quite a signficant amount of energy?

But I would imaging that after the first aplication of an olive and subsequent deformation then the risk asscoatiated with any subsequent re-sealing would only be incremental, the majority of the damage having ocurred on the first aplication, unless of course you ramp up the connection as hard as you can every time, but that would tend to be an extreme case.

cheers

David

I'm not a fan of compression fittings. It seems hard to make them water tight (or air tight as I pressure test with air first when possible) at installation. I've had a number of joints which never had an air-tight phase at any stage between the initial assembly and overtightening to the point of destruction. Conversely, soldered joints work for me first time, every time, and the end-feed ones look so much better where they are visible, so that's what I use unless circumstances dictate otherwise.

However, I've never had either a soldered or compression fitting fail after initial successful installation, which seems to be what this part of the thread is discussing.

Then again, compression joints on 0.5mm tubing are rather different from conventional ones.

"Grunff" wrote | Come on - where's your sense of curiosity? I know freak shows are | pretty non-PC, but this would be excellent.

What's the best power tool with which to sharpen the end of a pointy stick?

Owain

What I would expect to see on an X-ray is all the high spots welded - not a continuous ring.

There is quite a lot of energy in tightening a compression joint if it gets concentrated in a few high spots. The first time round will not be a problem as the olive will fill the voids - what I am worried about is on a second tightening the olive can move on the pipe leaving unsupported areas of compressed pipe where the polymer has been damaged in much the same way as polyester material for clothing is damaged as soon as it is cut.

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