We do some plumbing as well (coolant water for machinery) and the funny thing is that most of what we use is 1/2" connections. That includes the gear that comes from Germany and Japan. The only exception is the American manufacturer of the plumbing parts: for some parts only metric threads are offered! The logic of this wonderful world... [Linked Image]

We have a box marked "Weird brass fittings" where all unidentified threads go, like metric and NPT.

BTW, can someone explain why a 1/2" thread has a diameter of about 3/4"? [Linked Image]