A discussion on The Wall: 

Paul S. asked, "Has ever heard of screwed copper pipe? I have it on a job and sizes are way off. I guess it has the same OD as steel or brass screwed pipe.

K.C. Jones: Can't help you with it, but I have seen this. According to the tour guide when they need work done it's a massive pain for their plumber.

Danny Scully: My crew pulled this out of a bathroom remodel a few weeks ago. It's threaded copper! 1/2" copper threaded would be 3/8" ips.

 

Paul S.: This is what I had to deal with. The pic below has a 1.5" X 1.5" X 1.25" copper sweat tee. The 1.5" run of the tee is sweated on 1.25" threaded copper I thought it was copper sweat. I had to literally bang the threaded copper into the run of the 1.5" tee. I have a couple more connections to make. Do you guys recommend unscrewing it? Or should I cut clean and sweat or braze? I'm sure this is a stupid question, but it's definitely copper, right? Not brass? I would cut, clean, sweat or braze.

 

347: Don't if this helps or not. My dad started doing plumbing in the late '40s. When I was starting, he told me about the different types of pipe. Copper was L, M, K, DWV, BT (bending temper) and TP (threaded temper). I don't know how right he was, but he told me he used once very early in his career.

Steam Doctor: Maybe TP pipe. Don't quite know the history, but at some point when they were transitioning from galvanized pipe to copper, they introduced TP (threadless pipe). I think that it was copper with same OD as brass. You would need TP-copper adaptors. Have only run into TP twice. Not quite sure if my description of the TP pipe is accurate. Just what I heard from some old timers. TP can definitely be soldered. Be prepared for some sticker shock when buying adaptors.

Paul S.: It's definitely not brass. It was copper; the color was identical and not as thick as brass. Ive soldered or brazed copper to brass a few times before and it didn't get this easy. The solder just flowed perfectly. I originally thought it was lead-wiped copper joints because the joints do not look threaded. I looked for some sort of metal flow. Wen I cleaned it up, it was grayish. Thanks guys as always for your help.