Compression fitting question

[ladwey]

I'm having to work with both imperial and metric pipes and fittings in an old house. Earlier today I put a 15mm pipe with with olive into an imperial fitting, tightened it up, only to have it burst out when I turned the water back on. I had thought -- wrongly!! -- that because the imperial pipes will go ok into a 15mm fitting with a 15mm olive, the same would work here.

Anyway I cleaned up and found an offcut of the old pipe that had still had the old olive on. I put it back in and spliced it into the pipe run with a 15mm coupler, since I know that works. When I turned the water back on, everything held. My question is: if it doesn't fail straight away, does that mean it's going to be ok? It's not dripping or weeping, and all the other fittings are fine. But after seeing the other pipe shoot out I'm feeling pretty tense, and would like to feel certain that it's not going to fail in the middle of the night or something.

I know that eg soldering would probably be better, but there are access issues that make that very difficult. Thanks in advance for any help / reassurance --

 

[terryplumb]

15mm olive should work perfectly well on 1/2 inch pipe.
However a 3/4 olive would be needed on 3/4 pipe ,22 mm olive would not work.

 

[ladwey]

It's 1/2 inch pipe. Not sure why it failed. The nut is the original one from the old fitting, and taking a close look at it my guess was that the external diameter of the 15mm olive wasn't large enough somehow. It fit on the pipe well enough.

Where I've had to do the larger sizes I used imperial olives with 22mm couplings and it's worked great.

So if it's holding now and feels very sturdily attached, am I ok to go to bed without it flying off 4 hours from now and flooding the kitchen?

 

[terryplumb]

I assume the pipe is under mains pressure ? If it is, close your stopcock overnight if you are concerned.
It sounds like you didn't tighten up enough when it blew apart.
Old imperial copper is thicker walled and often harder too. You therefore need to tighten up the compression fitting quite a bit more than on soft,thinner walled copper.

 

[ladwey]

Might have been under-tightened, it was hard to reach. I thought I was really cranking on it! Always a tightrope when you're also trying not to over-tighten.

 

[terryplumb]

You could check tomorrow how well the olive sits on the pipe by undoing the compression fitting,and try to knock it off the pipe .
Rapping a spanner against the nut onto the olive. If it slides off the pipe easily it's a weak joint.

 

[ladwey]

Actually that was why I went back to reuse the section of old pipe -- the olive on it was absolutely rock solidly attached when I took it out of the fitting. That was what made me think it was a better bet to go back in. So that's a good sign anyway. Thanks for all your help here mate, I really appreciate it.

 

[CountryFan]

The existing fitting - could it be type b manipulative (flared)?

 

[ladwey]

Yes it's an odd shape -- comes down to a point at one end, broader than a normal olive at the other. If you took a cross section it would be triangular. I'd never seen one before!

 

[ladwey]

Just read this and it doesn't sound like what I was dealing with though ... It was an ordinary section of half inch pipe, no flared end, just a sort of pyramidal olive. I just assumed that was what olives used to look like back in the day.

 

[CountryFan]

Just read this and it doesn't sound like what I was dealing with though ...

View attachment 410603

That’s why I edited my original reply. As I re-read what you had put, doesn’t sound like one.

 

[ladwey]

Whatever it was had held for who knows how many decades before I got to it, so I hope it will still be sturdy now it's back in.

 

[terryplumb]

Sounds more like a cone fitting,rather than an olive that was used.
Pics would be interesting .

 

[ladwey]

I'm not taking it out again!! But I'll have a look in the morning and see if any of the other parts have one on. Some of the others fell apart when I took them out, but the one I reused cleaned up to nice bright copper.