Copper pipe compression fittings - rule of thumb?

Question

Just out of curiosity - I've come across various rules of thumb for copper compression joints eg:

finger tight then 1-1.5 turns,

or spanner until olive just grips then some random small amount more.

I only ask, because I used a cap off 22mm brass fitting today, which needed no more than 3/4 turn after finger tight to compress the olive into the pipe. It seemed to have a pretty decent hold after 1/2 turn.

Do they really vary this much? I seem to remember getting more turn on previous fittings I've used.

I disassembled it to check, being convinced it wasn't enough, but no, just right - olive nicely biting in without excessive deformation.

I even used a tiny smear of compound on the outside of the olive as lubricant.

Cheers

Tim

Dave Plowman (News) · Accepted Answer

Tighten then dry until they groan. Works for me. ;-)

David in Normandy · Answer

Previously I'd only ever used compression joints for the small amount of plumbing I'd done. That always baffled me too. Too slack and the joint leaks, too tight and the olive distorts too much... and it leaks. Nudge the joint... and it leaks.

Over the last few weeks I've done a fair amount of plumbing and learned how to use solder end joints. I'll never look at a compression fitting again - hideous things. Not a single one of my (80+) soldered joints leaked. They are also much more sturdy - not to mention vastly cheaper than compression fittings.

Donwill · Answer

I always substitute a copper olive instead of the usual brass one supplied, in the belief that the copper one is more easily squeesed on to the pipe.

Tim S · Answer

David in Normandy coughed up some electrons that declared:

I agree - most of mine won't be compression.

This one was capping off a gas pipe close to the meter - thus I can't solder without capping the meter itself, and whilst I'm happy with copper gas work, I'm not very happy pratting about with meter connections, though I noticed mine appeared to have a 22mm compression adaptor on, so I might revise that.

Yes, it did pass a full gas tightness test :)

Tim S · Answer

Donwill coughed up some electrons that declared:

That's a good point...

I've never had much trouble getting olived to work - I was just curious about rules of thumb for speed purposes, and why none of the rules of thumb seem to apply to joint I did yesterday. I thought the screw pitch was unified, which is about the only thing I can see that would make a difference...

Cheers

Tim

Copper pipe compression fittings - rule of thumb?

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