In article ,
Andy Burns writes:
harryagain wrote:

In general in the UK all pipework [...] is sized by the nominal
bore. mm comes from the EUSSR frogs

The frogs do tend to use myriad different sizes, e.g. for copper elbows
compare and contrast ...

http://toolstation.fr/shop/d110/sd2698/p39317
http://toolstation.com/shop/d20/sd2698/p86114

Although they call them something else, you will find their threaded
plumbing fittings are 1/2" BSP, 3/4" BSP, etc. This is useful for
buying thermostatic shower mixers, which are much cheaper in France
than they are here.

For copper tube, their equivalent of 15mm is 14mm, but unlike here,
many sizes are more commonly used too. (If you go to somewhere like
BES, you will find all the sizes here too, but you won't find them
in stock in a standard plumber's merchant.)

--
Andrew Gabriel
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