Doug Miller wrote:
In article . com,
wrote:

However if you know the nominal size you do know the OD, that
is unambiguous.

For a given material, perhaps. As a general rule regardless of
material,
definitely not: 3/4" steel, copper, and CPVC all have different OD.


After writing this:

http://groups-beta.google.com/group/...c?dmode=source

I was so sure you were confusing pipe with tubing that I
almost didn't look for this:

http://nrha.web-pros.com/How-To/plum...ipe/copper.htm

Amusingly enough the actual ID for copper tubing is ALSO larger
than the nominal size.

Copper and CPVC pipe indeed is made to a common dimentional standard
that is different from the ASTM standard for steel, SS, or PVC.

E.g. Two standards, ASTM D-1785 for steel (including Stainless), and
PVC, but ASTM D-2846 for copper and CPVC.

However, it appears that ASTM d-1785 refers to PIPE while ASTM D-2846
refers to TUBE, and the sources for CPVC refer to it as CPVC PIPE
in copper-TUBE sizes and far too many sources on the web use the
terms pipe and tube interchangeably for copper and CPVC. E.g.
according to THOSE people, pipe IS tube for copper, regardless of
the meaning of 'is'.

SO I think I'll stick with my earlier contention that the copper
and CPVC in your basement are TUBE (though 3/4" tube, not 7/8"
while the galvanized and black steel, and the PVC are PIPE for
those of us who distinguish between the two.

This looks like it might be a very good source:

http://www.pipefitter.com/Pipedatabk.html

--

FF