I'm currently planning a build with copper hardline tubing with 16mm fittings since 12mm seems a bit thin in a big case. The issue is, that there is only 15mm OD copper pipe in Germany, unlike the US where a 1/2 inch pipe has an OD of 5/8 inch (15,87mm). 15mm pipes do obviously not work with the 16mm or 14mm fittings. Does anybody know where one can get 16mm pipes without having to order several tons from China?
The 16mm fittings work with US standard pipe. Keep in mind that plumbing isn't made with exact tolerances. Some lengths could be too big or too small. That said, I had no problems with using it.
Thanks for the advice. Sadly the only 16mm or 5/8 inch OD pipe I can find comes from the US with about 200$ shipping cost. I'll try some local plumbers, maybe they have access to something like that. Otherwise, I will have to use 12mm pipe.
The UK sells 16mm copper pipe: https://www.bes.co.uk/copper-tube-16mm-x-3m-15658/ https://www.stevensonplumbing.co.uk/16mm-copper-pipe.html (cheaper, but sold in 1ft pieces only, not very useful).