22. The US and Russia Have Separate Water Supplies
In space, even the US and Russia are friends. So why do they have separate water supplies?
The U.S. uses iodine for bacteria control in the water. On the other hand, Russia uses silver for water purification. This just one of the many differences in the way these two space powers equip their astronauts.
If these substances mix, for some reason, a silver-iodine precipitate forms in the water. This can clog the sublimator in the NASA EMU spacesuit creating a tricky repair issue.
This is one of the reasons why astronauts need to do extra planning before international spacewalks.