Copper tubing in Taiwanese Trawler

So! What size copper tubing is it that will slip into an American 1/2" OD copper tube? As it happens, I brought scraps of both type L and type M. One's a bit loose. The other's a bit snug. Thinking I'll clean up the snugger and the Taiwanese copper and sweat 'em together like I knew what I was doing.

This is the 'permanent' repair to the clear vinyl tubing blowing apart episode.

3/8 OD Plumbers call 3/8 od 1/4" because they generlly only speak in terms of ID, HVAC people go by OD

M copper is a bit too thin for ID work as you found out.

The couplling would be in plumber speak; a 1/2 X 1/4" reducing coupling In hvac it would a 5/8 X 3/8" OD coupling.

M is copper's equal to thinwall. not likely enough pressure on a boat to worry about. There are sharkbite type fittings for both ODs available.

Your tubing cutter may have (or you can get) a wheel to make a depressed ring on the tubing but I'd suggest you use a proper fitting for sweating so the solder doesn't run past the joint. unless you braze the tubing slip joint.

Guessing this is the fresh water system?

Got away with soldering American tubing to the Taiwanese. The thicker wall American ID was a little sloppy on the Taiwanese OD, particularly on the hot water side (why ?). It took two tries for each end, while the cold fit better and soldered readily. (The hose clamp will be off tomorrow; it's what I used to keep the tubing in place while I hammered the failed joint apart...don't ask; it wasn't pretty or quiet!)

So, why did the hot side of the tub faucet give out as part of this adventure? And then, the hot side of the under-sink connection done with the same clear vinyl failed!

All is well, my son and his lovely, new, flexible girlfriend came down. He replaced the three last clear vinyl and she got her long arms and dainty fingers up to plug in the hourmeter!

Dinner for them was pleasant and cost less than an hour of paid techie!

Great job! For future reference, pex comes in the same OD sizes