Compression fittings.

[Department71]

Views please on 22 mm compression fittings UK supplied. Have just been doing a bit of plumbing and used a few of these, the ones with copper olives when tightened the olives gripped the pipe and wouldn't move. But when I used brass olives although the nuts were tight and the fitting water tight, when undone the olives were still loose on the pipe.

What have I done wrong if anything?

Cheers

Steve

[TefkaC]

Hello Steve, nothing wrong as long as the olive turns on the pipe with no movement along the pipe. As a rule of thumb a quarter turn on the fitting after the olive has gripped is sufficient, I know it doesn't seem a lot but try it.

Regards.

Charlie. 

[Gluestick]

Simply, copper is a very soft malleable metal and crushes onto the copper pipe. That's why they are a pig to remove!

Unless one has one of these!

See Here:

Brass (Alloy of Copper and Zinc) is much harder and far less malleable: therefore doesn't compress much.

With a poor fit up between the pipe and the olive, then brass olives can weep.

Liquid PTFE, or similar, normally solves this problem.

[Department71]

Thanks all for the replies. Did try and wrap a bit of ptfe tape around the pipe before sliding the brass olive over it, but it kept on rucking up so took it off and hoped for the best.

Might take it apart and wipe some of that plumbing mastic around the pipe, you know the stuff  in a tube you open once use a bit and when you try and use it again in the future its like rubber and you can't get it out of the tube!

Steve

[pachapapa]

The olive should be exactly at the end of a perfectly cut and filed pipe, if not the the pipe will be obstructed before the olive has been compressed into the cone and pinching of the pipe by the olive will not occurr. Once olive pinched one can disconnect the connection and reconnect again and no leak.

[Gluestick]

All olives should be correctly fitted and the pipe suitably cleaned and prepped.

The OP's concern was the fit-up between the pipe and a brass olive.

There are obviously, two separate considerations: the fit and thus seal between the outside surfaces of the olive and their mating to the chamfered faces of the pipe nut and the receiving fitting: and the interior fit of the olive to the pipe.

The inescapable reality is that brass is less maleable than pure copper: and another consideration is the proportion of Copper to Zinc in the brass: mass-produced extruded fittings do vary in dimension and finish. Furthermore, the very process of extrusion hardens the material.

In demanding applications (Hydraulics; oil pressure feeds, fuel feeds etc) the brass olives are normally soldered onto the pipe: which prevents seepage at the olive-pipe joint.

OP: use of such as Fernox LS-X or other jointing sealer is fine.

[pachapapa]

Never used copper, rarely brass on 8mm Cu, prefer PER.

[Anton Redman II]

Where did you buy the 22 mm pipe ?

Did you buy it as a coil ?

[Chancer]

PPP. On domestic compression fittings the olive sits back a litte way from the pipe end which engages in a spigot in the fitting, often this is slightly oversized due to the same fittings being used on 15 and 16mm pipes.

Sometimes due to poor installation the olive is flush with the pipe end but this could increase the risk of the joint failing when frozen, also any mechanical movement, strain etc could loosen the fit.

[Araucaria]

[quote user="Anton Redman II"]Where did you buy the 22 mm pipe ?

Did you buy it as a coil ?[/quote]

Brico Depot sell 22mm copper pipe and compression fittings for it. It is possibly available there as a coil, but what I bought in the Rodez branch was the (hard) straight lengths. From memory they had it in 2m and 3m lengths. If you need to bend it you'll have to anneal it first.

With compression fittings, I don't think you should ever try to get PTFE tape between the pipe and the olive. The olive is supposed to compress and make a very close fit on the pipe, and stay there once compressed. You can use it round the outside of the olive, though if your fittings are well made and everything is nice and clean you shouldn't need to. However, if the joint leaks after tightening up without PTFE tape, you can always try a bit of tape round the olive on your second attempt.

[Department71]

Hi all, have to admit the job in question was done in daughters house in Basingstoke, not France this time. The pipe is normal UK spec 22mm pipe, the fittings would have been sourced from Screwfix.

The pipe was pushed fully into the fitting so the olive isn't at the end of the pipe. Have had a second look at the fitting and so far no weeping. She needs a new boiler so will  re do  when system is drained.

Cheers

Steve

[BIG MAC]

Back nut onto pipe then slide olive on in approximately the right position ...wind a little PTFE round pipe and slide olive onto it to retain it then another few turns of PTFE round the olive itself. Slide fitting body on and push the pipe into it so that the olive sits securely on the chamfered seat. Fit backnut and tighten.

The PTFE under the olive promotes its grip on the pipe and creates a compressed plastic seal on the mating faces....simples