Basic plumbing - compression joints.



How you you work that out? Any old copper pipe can be cleaned to perfection, and solder will fill any gaps. Obviously you have to make sure there is no water in the pipe close to the end.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On 19/06/2018 14:01, Dave Plowman (News) wrote:

If you're making a joint on an *installed* pipe - as the OP is - it is often difficult to get access to clean it completely, particularly if it's got paint on it.
A compression joint with a smear of LS-X or - if you prefer - a wrap of PTFE tape can cover a multitude of sins.
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Roger
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You need it to be clean for a compression fitting to work too.
But a cleaning strip works well on a pipe close to a wall.

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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Tuesday, 19 June 2018 17:30:16 UTC+1, Roger Mills wrote:

it can't cover many sins at all, there lies the problem. Compression & solder cover different sins, neither does them all.
NT
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IANAP If the olive and fitting slide over the burrs left by your hacksaw, just fit it and you'll be fine. I suppose you should consider if the pipe is old enough to be an imperial size.

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Tim Lamb

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Yes! Although the house is Victorian, most of the plumbing was installed +/- 40 years ago, so a fair chance it will be metric?
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A compression joint shouldn't have any compound or tape on it. It's designed to seal without anything added to the sealing faces. (In the case of carrying gas, it *must* be assembled according to the relevant BS, i.e. without any sealing added.)
However, if it's been buggered up by fitting badly, then the seals may not work as designed, and can often be bodged by using tape (again, not acceptable for gas). This will not seal for as long as a properly made compression joint. Once the seals have been contaminated with something, it will probably always need bodging to make it seal again because the sealing faces are damaged.
The most common way I see compression fittings damaged is by doing them up using a poorly fitting spanner on the compression ring. This can distort the compression ring into an oval or egg shape, and then it won't seal, and may even leak more as it's tightened. The spanner needs to be a good tight fit so there is no tendancy to roll over the nut corners. The jaws need to be parallel, and if using an adjustable spanner, they must stay parallel under force (cheap adjustables don't). I do sometimes use a single turn of PTFE on the non-sealing half of the olive as a lubricant while tightening and compressing the olive on large pipe sizes, but if you do this, make really sure it doesn't get into the sealing surface of the joint, and after initial assembly which compresses the olive, you can disassemble and remove the tape.
If the capping off is temporary, I will often do it using a pushfit end cap (although they don't like being pushed onto hacksawed pipe ends with any burr as it can damage the O-ring). When doing plumbing, it's good to have some pushfit endcaps to hand anyway in case you have to cap something off you hadn't thought of (e.g. water trickling back out the other end of the cut pipe).
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Andrew Gabriel
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On 17/06/2018 09:34, Andrew Gabriel wrote:

I have a small collection of speedfit stop ends for just this purpose... I find them handy as they are easy to remove by hand without needing tools.
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John.
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Both work fine. I prefer tape myself.
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On Sunday, 17 June 2018 07:35:17 UTC+1, Graeme wrote:

A dry compression fitting should seal, but doesn't always. A bit of gloop in there can solve that.
If you're new to this, do the nuts up good & tight. It's surprising how much tightness is needed.
NT
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On 17/06/2018 07:35, Graeme wrote:

More than likely...
My experience is :
Generally if the pipe is clean and in good condition (not scratched, dented etc), then a compression fitting will seal just fine on its own.
Using some lubrication on the threads to make tightening easier (especially if working in a confined space) can make the job easier. A pipe jointing compound like jet lube will do the trick, but so will a few turns of PTFE tape on the threads[1].
If for some reason you can't get a good seal on a joint (maybe 1 in 100 joints IME), then a few turns of PTFE over the olive will normally fix it. As will application of a jointing compound. (use a proper WRAS approved one though - not something that will harbour microbial growth like putty or old school boss white).
lastly a decent set of spanners help enormously. Using something that is poor fitting can in extreme cases deform the backnut, and that will have difficulty ever making a proper seal.
[1] You will hear people bleat on about that being "pointless" and "amateur" etc, but that is because they are too dumb to understand that lubrication of the turning bits has a completely separate purpose from augmentation the sealing surfaces with similar materials.
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Excellent. I have completely cleaned and almost polished the pipe where I want to cut, and no signs of any dents or deformity.
<much useful info snipped>
Will report back :-)
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On Sunday, 17 June 2018 07:35:17 UTC+1, Graeme wrote:

Angle grinder. Plus file to deburr it. You may find it's imperial not metric as well.

Whatever you have to hand
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Good advice I picked up on this group was to pull the pipe back a couple of mm before tightening the nut. This allows the pipe to "pull in" as the nut is tightened.
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Noted, thanks.
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Graeme

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wrote:

Isn't this one of the very instances we bought our multitools for? ;-)
Cheers, T i m
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On 19/06/2018 21:23, T i m wrote:

They are good for thing like plunge cuts into a pipe surrounded by others. I tend reach for my small 10.8V reciprocating saw for most plumbing cuts that I can't do with a pipe cutter since its much faster and the blades are cheaper and more robust.
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