Identifying 3/4" copper from 22mm copper.

[Soulmonger]

I'm a kitchen fitter first and foremost, so occasionally encounter old pipes of varying sizes. From past experience I know how easy it is to misidentify old 3/4" copper pipe (apart from getting soaked when you get it wrong) and would like to know if there is a surefire way of telling it from 22mm pipe. I know a couple of old plumbers who can tell it on colour alone, but even with an olive of each size I'm sometimes uncertain. Would measuring the pipe o/d be a definitive test or is there a better way.
Thanks in advance for your help.
Cheers.

 

[fowlerboi]

Carry 3/4" to 22mm couplings and 3/4" olives to put in compression fittings and then never be caught out.

If you mean that you sometimes pipe it up and then realise only when you're turning the water on then do you not feel/see the fittings are loose? I get plastic is a little more difficult for that but they still flap around in the breeze and slip onto the pipe far too easily to make any seal

You can normally tell it apart because of property age and the colour is a very dark copper as its been heavily oxidised with age, you may even tell from the fact someone has worked on it before and it looks peppered with fittings all in a row. Tube wall thickness is another as its typically a lot thicker than modern 22mm tube

Best way to test is stick a 22mm end feed fitting on it and it will be loose.

 

[Podengo]

Get yourself some digital calipers, they are under £20 for decent stainless steel ones.

I can't remember the diameter but it's about 1/4 of a mm from memory.

Also the imperial stuff has a thicker wall, whereas 22mm is 0.7mm thick I think.

 

[Soulmonger]

Thank you Fowlerboi for your reply.
In general I try to avoid push fit fittings, so would always plump for e/f or compression. The wall thickness seems a good idea but it's sometimes hard to see in tight places. I always carry a few 3/4" olives since it can be a right pain when you suddenly need one and you're in the middle on nowhere. Usually I try a 3/4" olive on the pipe first if I'm unsure but even then they can appear loose sometimes. Only coming across 3/4" occasionally means that I never really get the experience to identify it on sight alone. I always have this deep feeling of dread when turning on the water again.

 

[Podengo]

Thank you Fowlerboi for your reply.
In general I try to avoid push fit fittings, so would always plump for e/f or compression. The wall thickness seems a good idea but it's sometimes hard to see in tight places. I always carry a few 3/4" olives since it can be a right pain when you suddenly need one and you're in the middle on nowhere. Usually I try a 3/4" olive on the pipe first if I'm unsure but even then they can appear loose sometimes. Only coming across 3/4" occasionally means that I never really get the experience to identify it on sight alone. I always have this deep feeling of dread when turning on the water again.

I've found suitable sealant like fernox LSX or flomasta will generally seal a 22mm I've on 3/4" although the softer copper olives squeeze up better than the harder brass ones.

My house seems to be a mixture of 3/4" and 22mm so I never know what I'm gonna find under floorboards

 

[Soulmonger]

Thanks Podengo, that seems the safest way to proceed.
Did you mean a 1/4 mm difference in diameter?

 

[Soulmonger]

I've found suitable sealant like fernox LSX or flomasta will generally seal a 22mm I've on 3/4" although the softer copper olives squeeze up better than the harder brass ones.

My house seems to be a mixture of 3/4" and 22mm so I never know what I'm gonna find under floorboards

The first time I encountered 3/4" pipe I didn't realize that it wasn't 22mm, I fitted and isolating valve and the pressure shot the valve across the room, so you can understand my hesitancy, mind you it was over 4bar. I use LSX every now and then so always have a small tube knocking around.
I will get a pair of digital calipers and be better prepared.
Thanks.

 

[SimonG]

Can tell its 3/4" as soon as you put a 22mm end feed fitting on it.
As above, carry 3/4" x 22mm soldered reducers and 3/4" olives.

 

[Podengo]

I fitted and isolating valve and the pressure shot the valve across the room

I can see how that is etched in your memory

4 bar of pressure on an open ended 3/4” pipe can spray out a lot of water in 30 seconds….so I hope the stopcock was nearby

 

[ShaunCorbs]

22mm fittings will say 22mm on them most of the time the 3/4 ones won’t have any size on them

 

[Soulmonger]

The stopcock wasn't too far away, but far enough for a small swimming pool to form. Thank you folks for your help, it is invaluable.
I particularly like the end feed 3/4" to 22mm reducer idea, I shall get some post haste.
Cheers.
I may well post again.