Imperial olives measured internally ?

[flutterbye]

Finally getting around to replacing an old stopcock on what I'm pretty sure is alkathene 1/2" pipe (it measures 21mm externally). Currently the cold feed goes into the existing old stopcock which connects to 15mm pipework.

I want to buy an new olive for this pipe. Do you think I need to buy an olive that is advertised as 1/2" or 3/4" ? I mean I'm thinking that if the imperial olive is also measured internally than 1/2" sounds right but if measured externally then its the wrong olive ?

Also, should I get a copper or brass one?

Something like http://cgi.ebay.co.uk/10-x-1-2-TUBI...aultDomain_3&hash=item415632552b#ht_500wt_942 ?

Thanks in advance for any advice.

 

[bengasman]

The only times olives are compatible is when you use 15mm olives on 1/2" copper pipe, and 28mm on 1" copper. It might be a bit hard to get it done, but it works as the imperial pipes are fractionally ( microns ) bigger than their metric counterparts.

 

[muggles]

Cut the pipe off just below the olive and use a Philmac stopcock with an adapter to copper in it...

 

[Weedrip]

If you do need to replace the olive on the alkathene then yes a 3/4" imp olive is what you need.

A 22mm brass stopcock with reducer to 15 on the outlet is best way to go.

A Metal fitting over plastic wins every time for this type of fitting in my book, and don't worry the 22mm stopcock will work with the imp olive, have fun.

 

[flutterbye]

Thanks all. So to be clear, when talking about 1/2" pipe, you need a 3/4" olive?

(Why not a 1/2" olive for a 1/2" pipe) ?

 

[Weedrip]

Its about understanding the historic conventions of pipe sizing.

Some pipes were defined by their Inside and others by the Outside measurements.

All part of the black art of plumbing