How do they get potable water on nuclear submarines that are underwater for long periods of time?
I feel bad for not finding Answerbag four years ago. There are three main methods of making potable water on nuclear submarines. 1) Steam evaporation. Steam from the steam plant is used to boil sea water. The evaporated water is recondensed back into potable water, as the salt soes not evaporate with the water. 2) Electric still (distillation). Same principle as the steam evaporator, except the heat is supplied by electric heaters. 3) Reverse osmosis. Uses the principles of osmotic pressure to force highly salinated water across a semi-pemiable membrane using pumps to maintain a high cifferential pressure across the membrane. This high pressure reverses the osmotic migration of the salty solution and forces the highly salinated to one side of the membrane and purer water to the other side until eventually only pure water is left. A little more than that to it, but good enough for this explanation.