Tiawan Copper Pipe Size

[Rocky Champagne]

Suffered a split, copper water pipe in my 1984 Sundowner Tug during recent heavy freeze. At first it appeared to be standard 1/2” O.D. so I tried a Sharkbite fitting and it was too loose. I looked at standard compression fittings and the 1/2” collar was too small and a 5/8” collar was too big. I measured the pipe and learned it is Imperial standard of 15 mm. I found the correct size fittings at Hamilton Marine. Just thought this would be a good piece of information to have. Rocky Champagne, 1984 Sundowner Tug, 36 ft. Hull #13.

 

[Alaskan Sea-Duction]

Same here. A 1/4 inch or 3/8 worked for me. For the bigger tubing I used 3/4.

 

[Insequent]

I was curious about your description of "imperial" and "15 mm", as the latter is obviously metric. But here is a link to a table that kinda explains it:
Pipes and Tubes - Imperial vs. Metric Sizes

I guess some refer to OD and some to ID