Joining copper pipe and the Wiki

[Tim Watts]

I might be blind, but is there a Wiki page on copper compression fittings?

I have to embark on another round of plumbing and I wanted to check something.

The something is:

What's best practise for tightness of fittings?

I usually do mine up with a brass olive until there is the slightest hint of it biting into the pipe - you can see a slight deformation on the inside of the pipe if a torch is shone in just right. This equates to about 3/4 to 1 turn after the nut is finger tight.

Theory being the olive cannot possibly slip off. Not had a problem to date doing this - but was curious to see what others considered best practise.

[Andrew Gabriel]

That's probably what I do too, although I don't actually measure it; I just do it up until it starts getting tight, and then turn it some more.

The important thing is using an appropriate spanner. If you use an adjustable spanner with parallel jaws, the jaws mustn't spread when you put force on them or the spanner will ride up the nut corners and turn the locknut into an oval shape, and it will then never seal. Similarly, a fixed spanner must be exactly the right size (which is tricky as the across-flats dimension is not standardised, and varies between makes and sometimes even between fittings).

Also, don't put anything on the sealing surfaces. Providing it's not gas pipe, you can use lubricant on the non-sealing surfaces such as the thread, and this can ease the initial assembly of larger sizes of compression fittings in particular.

[The Medway Handyman]

I believe the technical term is "a bit more welly".

Two of the best things I ever bought;

and;

+1

[Tim Watts]

Thanks Andrew.

No, I never use any sealant. Except boss green (*spit*[1]) if remaking a very old joint and it just won't stop weeping.

[1] Horrid stuff, but Boss White is no longer allowed on potable water.

My first few joints I actually took apart until I could see the olive had bitten and so had some idea of how tight was right (this was 22mm).

The bad experience I had was actually a bit stupid but made me wonder if olives might drop off pipes. This was an MDPE-copper compression adaptor. The MDPE side was fine - large thin olive, insert and lump of brass with thread and nut on one end. Not thinking and not having seen one of these before, I tried to stick a compression joint on the other end. It went really tight on the bench - seemed solid. Then I dropped the fitting and as it hit the floor, the coupler just fell off - it was actually quite loose - because although the olive had tightened, the brass had no give for it to bite.

Naturally I realised I was a plonker, thanked Mr Murphy for not letting me get as far as actually installing it and soldered a stub of pipe on before I made the MDPE joint.

Did make me wonder therefore if it was possible to get a "tight" joint which actually wasn't...

[Tim Watts]

I have one of those :)

Looks interesting. I have 2 adjustable slim but quality spanners that have not failed me yet.

The number of people on other forums (Screwfix *cough*) who plaster everything with Fernox LX.

[Tim Watts]

While we're on the subject - soldering...

I have a pipe iron for those areas I really don't want to be waving a blowtorch around such as near bundles of wires and tight in the roofspace near celotex.

It works just fine - slow, but not too slow and is modern enough to handle unleaded solder.

Problem is the ends keep dropping off when it's hot, despite the little metal shims.

Needless to say this is a bit of a liability as they are heavy, solid and fecking hot!

Anyone had experience of getting these to stay on?

Drill and tap some small brass screws in to each head might work, but would need to be careful not to put too much pressure on the element rods...

More or thicker shim sheet might also work but not sure what to use - apart from maybe butchering a set of feeler gauges.

[dennis]

They don't have to dig in. If they have dug in you have over done it.

You probably used the wrong olive.

[meow2222]

The 2 metal surfaces digging into each other is how they seal. Surface deformation zeroes the gap. What is the wrong olive? AFAIK copper and brass both work fine, but I'm no plumber.

NT

[meow2222]

No. Anything people write here can be put on the wiki if the person gives permission to do that. Otherwise it can't.

NT

[meow2222]

A start:

NT

[Tim Watts]

Let me put it on my list then. I *have* to do some plumbing in the next

4 weeks (kitchen fitting, need the water main route finalised, it's a bit of JG Speedfit flapping around right now in the wrong place).

I can get some photos, do a draft - it will be a very singular and narrow view - but I expect others will be happy to widen the content :)

[Tim Watts]

In what sense "wrong"? If you mean I mixed up imperial and metric - no, not a chance.

[Tim Watts]

Although copper olives do up more easily, I made a decision to throw them away and use brass - because I think a soft olive on a half-hard pipe is likely to be less effective. But i could be wrong.

[Andrew Gabriel]

No it's not. It talks about using sealants.

[Chris French]

In message , Tim Watts writes

I use whatever there is, can't say I've ever noticed any difference.

Though one is better than the other when using a compression fitting on plastic pipe - though I forget which is recommended

[Capitol]

I guess I'm in a minority of 1 here. I always use gas ptfe tape and HMP grease over the olive and on the threads. In 50 years, I've not found any problems of leakage and the joints always come apart without difficulty.

[Adam Funk]

I'm going to show my ignorance here. Why not on gas pipe?

(I used to use Boss something, probably green, for water, but now I just use PTFE tape because I inherited a box of it; I noticed it's what the excellent pros I hired earlier this year used too.)

Don't worry, I don't do gas. (Well, you know what I mean.)

[meow2222]

Lots of people use various kinds of sealant with metal olives. I typically use linseed putty on old pipe. As the article says, opinions tend to be polarised.

NT

[Tim Watts]

Old I agree with - I have *had* to do that when a modified joint just refused to seal.

Fresh joints definitely should be done dry[1] unless they refuse to play ball, IMHO - but it's a point of pride Probably because I've seen ultra high vacuum equipment in my physics course - the sort of vacuums where the leakage of air through glass walled tube becomes something they actually start to care about

Well not quite unless there's a lot of helium about, but you get the point

I've never seen sealant used there - most metal-metal joints are done with a series of sharp lips milled into the mating face of each stainless steel component and a soft copper sealing ring is sandwiched in when the bolts are put in and done up.

So in theory metal-metal joints, done right, are the best.

The other time I have seen a iron-iron flat faced joint is on a steam loco boiler. Those joints are hand scraped dead flat using a reference and engineers blue. They seal with no compound, because compound is deemed unsafe due to the possibility it will blow out under pressure.

I expect they rust together pretty quickly too

[meow2222]

When you say best, it looks like that means capable of very low gas leakage under vacuum. Domestic plumbing has rather different requirements, namely adequate watertightness despite the real world surface defects that occur. Hence putty etc has its uses.

Since I deal more with old pipes than new, and got fed up with too many failures, puttying olives is pretty much the norm for me. The result was a great improvement in success rate to close to 100%.

very different to domestic plumbing though.

NT