First compression fitting - water through ceiling...

[PhilipW]

This question has been posted 1000 times and probably with as many different answers, but I screwed up today so I'd like some input please.

I'm a home diyer. I've installed kitchens, tiled floors, fixed cars, fitted taps, replaced thermostats and loads of other jobs but I've never had to do a compression fitting. I found out why today. Is it really just a matter of experience to get it right?

I replaced a double-check valve on my external filling loop today because, after 11 years, the iso tap was leaking. Tesla kit (because I wanted a pressure gauge), new olives etc etc. But it took me 4 goes and it's still weeping. One of those, because I was trying not to tighten it too much, I left it too loose and the mains pressure blew the new valve off - water all over the airing cupboard, dripping through a light fitting downstairs. All fine now - second beer...

But seriously - some say 1/4 turn after hand tight. Some say 1 turn. I struggled to get it past 1/4 turn with a big wrench. Some say PTFE around the olive (which is what I did in the end), some say JetBlue etc, some say only dry. So, once again, is it really just a matter of experience? Once you know, you know sort of thing?

 

[Iwilldoit]

From what I know listening to pros is that they are designed to be dry but they use a bit of paste and never get a call back. Make sure the pipe is fully inserted and not scratched / dented hold body with grips whilst tighten nut, build water pressure up slowly dont just whack on and look for weeps and tweak up nut until weep stops then increase pressure - check for weeps -- my extra rule is never do it just before you go bed or in the evening but to do it when you be around to keep checking it.

 

[CountryFan]

I had a bad experience with one once, and I’ve been doing it for years. I ended up using ptfe tape, and I still think it was weeping. I think I ended up using a whole new piece of copper. Sometimes the pipe/olive can be distorted. Usually if you’re making a new joint, it’s dry only. If you’re re-using an olive sometimes I’ve had success without additional measures and other times I’ve had to use jointing compound, ptfe tape or more recently ls-x.

 

[PhilipW]

Thank you chaps. Really appreciate your replies. So it's not a "one-size-fits-all" then and it actually is a matter of experience.

I've definitely learnt the lesson of not doing what you think will be a quick job, in the evening after a day's work, because the quick jobs are never that!

I think the pipe was a bit scratched so actually I probably should have cut the top of the pipe, cleaned it up and then put the new fittings on, with jointing compound for belt and braces.

Really useful and made me feel much better! Thanks again for taking the time to reply.

 

[blup]

Use brass olives

 

[robinbanks]

Use speedfit/hep2o

 

[jj4091]

Use brass olives

I always thought copper ones gave a better seal because they were softer and filled in defects in pipes and fittings. Must admit though it's a long time since I've used any so perhaps my memory is playing tricks on me.

 

[johnny2007]

Agree on brass olives.
Personally I think it's just a matter of feel.
Every time I fit a compression joint I wonder how come nobody has yet not made a rule about ideal torque.
Possibly because different brands of copper pipes, fittings and olives require different torque?

 

[Exedon]

Always a smear of jointing compound that's correct for what your doing.
If reusing existing nut/olive make sure mating surface clean maybe a wrap or two of ptfe on olive.
I use a 8in bahco adjustable on 15mm nuts if I wanted to could over tighten even with that..
Tend to see more copper olives crushed up but that's probably because they are softer.

 

[Iwilldoit]

Its easy to damage the pipe by overtightening so its best if you are not sure how tight (like me ) to nip it up a bit if if weeps, but yours seems to of gone stroboscopically wrong - like you never even tightened it at all if it blew straight off

 

[jj4091]

Agree on brass olives.
Personally I think it's just a matter of feel.
Every time I fit a compression joint I wonder how come nobody has yet not made a rule about ideal torque.
Possibly because different brands of copper pipes, fittings and olives require different torque?

Probably because nobody makes an adjustable spanner or pipe grips with a built in torque setting

 

[foxhole]

Usually use gas tape , only needs 1 and half wraps and not had a leak with it .

 

[Roberto2019]

I use brass olives if possible, tighten up until you hear a squeak (so pretty tight).... never had a problem. No tape or anything.

 

[ATTQ]

I don't wire wool the pipe shiny like i would for soldering, the original finish is nice and smooth and I always use a smear of jointing compound because why not. Then a good bit of force to tighten, I've never managed to cause a leak by over tightening so tend to just go for it with normal sized spanners. If the idea is to crimp down the olive it has to be a good bit of force