Compression Joints

[richard978]

Working with a contract heating engineer today and a couple of his rad valves had minor leaks. I attempted to nip them up but they were so tight I couldn't.

I removed one of the TRVs and the copper had been severely crushed. I then tried telling him that he was overdoing it and it really should not need that much to make them water tight. I then got the man and boy story. He then belted them up even more and to my astonishment they stopped leaking.

I was always taught about half to a full turn on compression joints, at least that was what I can remember. What is everyones else's views on this

 

[Chalked]

You can't do it by tightening up by measuring 1/2 a turn etc.
It depends on the type of fitting and olive. A hard brass ring will always need to be tighter than a copper ring and a nap type thread will need more force to tighten than a fine thread. Also depens how big your spanner is!!!
Always put a smear of jet blue on

 

[joni os]

Tight enough to crimp the olive to the tube and not much more. For me it's a matter of feel rather than a prescribed rotation. If you go light you can always give it a bit more until you get it right.

 

[richard978]

Tight enough to crimp the olive to the tube and not much more. For me it's a matter of feel rather than a prescribed rotation. If you go light you can always give it a bit more until you get it right.

That's always been my view. The reason I ask is that guy was having none of it. I started to question myself because this is a guy who been in the trade for 40 years.

I just tighten until it feels tight. If I get a weep I nip it up...and its always worked

 

[ShaunCorbs]

That's always been my view. The reason I ask is that guy was having none of it. I started to question myself because this is a guy who been in the trade for 40 years.

I just tighten until it feels tight. If I get a weep I nip it up...and its always worked

FT and nothing else and ive cracked a new nut and fitting before now

 

[Leo21]

It's all about the feel, the only weeps I get are with rock hard brass olives. I'm not keen on copper olives, they leak easier when knocked.

 

[Best]

The 40 year in the trade guy is an idiot. Ignore him. Everybody has their own ideas or habits about how to do things, - often begun from copying whoever we worked for when we started.
Truth is you can't always know how all fittings are tightened properly. Some of the odd stuff, - like specific valves, come with fine threads & hard brass olives.
I always use jointing paste and prefer good quality brass olives for most jobs, especially hot pipes, but obviously not to plastic pipes where it would be a copper olive. The jointing paste is a fine sealant which will lubricate the joint also and it prevents microscopic leaks, - something that a lot of plumbers seem to not realise happens. I use Jet Lube. Expensive, but doesn't set, no waste and does potable water or gas.
The olive should be compressed a little and not crushed into the pipe, which will damage the olive plus squeeze the pipe in and mean the olive is not contacting the fitting taper in correct place. Common sense really and something that guy has forgot to use in 40 years.

 

[lame plumber]

40 years adds up to a lot of leaks

 

[oz-plumber]

As for tightening up olives and compression joints, I use the 'feel' method as well.

I tighten them up until I 'feel' the spanner is about to break.

I have been to so many radiator leaks that are caused by the pipe to valve connection not being tight enough. If the olive doesn't crimp onto the copper, there is nothing holding the pipe in place.
As for hot and cold water connections - have seen many pipes slip out of the fitting / valve due to not being tightened up properly

 

[gassafe]

The joint your boss wrenched up even more will start to leak again as its now a poor joint! The plumber will have to cut the pipework back & resolder a new piece too... See it loads when swooping trv's!

 

[Stigster]

I have a long standing argument with one of the two lecturer's I support training the City & Guilds 6035 and also schools links students. On a 15 and 22mm the fitting should be done up finger tight and then about 270 deg. further with a spanner.

He believes that the tighter the better. I disagree.

We did a test where I used my method and he used his and tested to 25 bar. To be fair neither leaked but his was done up so tight it was difficult to undo again, the copper olive was extruding out the top of the nut and the pipe was visibly distorted if you looked down the tube.

I won't name him but this type of overdone fitting is now known as "Stevie tight."

As for paste, that's personal preference and everyone and his dog has an opinion on that! I don't use it myself, preferring to only use a couple of wraps on the olive if I have a problem. To each his own on the pastes/compounds.

Out of interest, I decided to try to make an olive purely out of a load of wraps of PTFE and did up the nut (Stevie tight this time) and it held all afternoon at 6 bar! This was just an experiment and not something I'd ever actually do but it was interesting to see how well even that sealed.

 

[Best]

It all depends on the fitting, the threads on the fitting, how tight the threads are on nut/fitting, what type of olive and what sort of pipe you are tightening onto. All these idiots in training places are only doing a general advice.
Olive should compress but also grab pipe. Soft brass olive, round type or else good taper is best for most things except plastic pipe or gas I guess. Paste is essential as it is a fine sealer.
I know all this because I am fussy and that is the way I always do it and I don't have any slight leaks, even if I go back many many years later. Doing maintainence jobs and private work taught me this.

 

[Stigster]

I agree with what you say, Best.

I don't get out a protractor or anything, I just do it by feel, but as a rough guide for newbies it's better to give some instruction other than "when it feels right." I know what you mean and it's just not even something most of us think a lot about, just do it.


Edit just to add, thankfully we have a States of Guernsey registered apprenticeship scheme running for many years on the island. Apprentices, all of them, are in full time employment for five years, coming to college one day per week to do their practical and theory portfolios and exams.

Not a fast track system. Unfortunately I can't convince one lecturer on his over tightening of comp. fittngs.

 

[Best]

Tell your lecturer that by over tightening the fitting the olive is being misplaced and squeezed away from the fitting taper and pipe is being damaged permanently. In other words, olive is is wrong position.
There is a better way to compress fittings IMO and the way I was taught, but I am keeping it to my self. :smile:

 

[Stigster]

I've been over it so many times with him. He just won't have it. He's paranoid that over months/years the fitting will slide down the pipe.

Even massively over pressurising a correctly tightened fitting (25 bar) didn't convince him. He's a good guy and a good teacher in many ways but not on this one. I've explained he's clearly damaging the joint but like I said, he won't have it.

The other problem is that it's my job to take the stuff apart and re-use what we can. He's even made the nuts oval on some of them. If the fitting distorting won't convince him nothing will.

I even showed him the instructions from Prestex. He's in I know best mode.

 

[Best]

Sounds like he is a 'Can teach it' but 'Can't do it'
Typical expert in a classroom.
No brass fitting will come off by itself if olive has a little grip on the pipe. You could remind him that while the nut remains fully tight, the olive has extra compression against the pipe & fitting.
Why he is going against what every manufacturer instructions say and just about every plumber says, shows incredible arrogance and, frankly I would worry about anyone taught by him.
Surely being able to do joints properly is the most basic starting point on plumbing.

 

[gassafe]

Good job he ain't a mechanic, he would probably air gun the wheels onto cars to death so that they never came off again!!!

 

[newcastle phill]

Well you dont want them falling off [emoji12]