21mm copper pipe ??

[namsag]

Can you explain how something smaller than 22mm can be a tighter fit than something designed for 22mm

 

[Nige F]

ask a gynacologist

 

[powell30]

Can't....just that it is, at least where i have experienced it

The actual pipe wall is a lot thicker on the 3/4 tube i have encountered hence tighter fit

 

[namsag]

Like everyone else on here who is surprised by your findings . I have never came across 3/4 copper that is not slack in any type of 22mm fittings.
Now 1/2 and 15mm is the other way and is 1/2 is tight in 15mm fittings and no prob.

Apart from the 1/2 copper i came across once with walls that thick the fittings where cut and threaded .

 

[powell30]

Then maybe my recollection is clouded by age and it was the 31 coats of gloss that brought it out to 22.4mm.......

 

[ManxPlumber]

Any 3/4" copper pipe I've encountered was smaller than new 22mm pipe, as proved by fitting a 22mm yorkshire fitting, I usually resort to using a 22-3/4 yorkshire connector

 

[MikeAustin]

I have just come across a similar incompatibility. I have had to re-solder a 22mm hot water piper into a old T (not the best solution but the most practical, and it is water-tight so far). On removing the old pipe, the new 22mm pipe would not fit. I had to re-use a short, clean length of the old pipe. The old pipe is 21.5mm OD, which I am guessing needs a 3/4" olive in a standard 22mm compression joint.
I don't know how the imperial system compares with the metric, but the old cold water pipes and joints all seem to be compatible with new 15mm. Does it just happen to be that the pipe wall thickness means that 1/2" ID is equivalent to 15mm OD?

 

[doitall]

3/4 is a tight fit onto a pushfit fitting. If anything it is more secure than onto a 22mm pipe.....and yes it is not recommended, and yes sometimes the fit is too tight and you pinch/split the rubber seal.....it was just another suggestion. In an ideal world end feed 3/4 to 22mm or 3/4 compresssion olice.....

¾" is smaller than 22mm so will flop about in a pushfit fitting and blow off as soon as the pressure was up.

 

[swbjackson]

3/4 is a tight fit onto a pushfit fitting. If anything it is more secure than onto a 22mm pipe.....and yes it is not recommended, and yes sometimes the fit is too tight and you pinch/split the rubber seal.....it was just another suggestion. In an ideal world end feed 3/4 to 22mm or 3/4 compresssion olice.....

3/4 pipe is smaller than 22 so how can it be too tight in a 22mm pushfit fitting?

 

[Whitespirit66]

WARNING - 4 year old post raised from the dead.

 

[Delie]

¾" is smaller than 22mm so will flop about in a pushfit fitting and blow off as soon as the pressure was up.

This isn't true. As a complete amateur I've actually had a push fit (speedfit) 22mm isolation valve on a 3/4 pipe for 2 months without realising and it didn't blow off. It was only when I went to put on a 22mm compression isolation valve that I realised I was dealing with old 3/4 pipe. I felt lucky nothing went wrong to be honest, but don't assume the push fit fittings will just blow off, because they may well not do that, just as mine didn't. I've tried and tested it by accident ... i wouldn't' do it deliberately though

 

[Dan Robinson]

Like we're willing to bet our insurance premiums on blinds luck and ignorance?

 

[Delie]

yeah, that's why i said i wouldn't do it deliberately

 

[doitall]

yeah, that's why i said i wouldn't do it deliberately

Obviously you didn't put much pressure in the pipe

 

[Delie]

Yes, I suspect you are correct there. As I say, I think i was lucky to get away with it for so long to be honest. Soon as I realised what was going on (when I put a 22mm olive on and realised how loose it was) I bought a 3/4" to 22mm coupler to sort it out. I was amazed it had managed to last that long without blowing off

I didn't know about these metric/imperial issues until I moved in to my current house which was built in the 1930's