What is reverse osmosis water?

Answer 1

Reverse osmosis, or RO, water is water that has been purified using reverse osmosis techniques. Osmosis is something that occurs naturally, it's when a solvent (something that is dissolved in a solution) passes through a semi-permeable membrane from an area where there is a lot of it, to an area that does not have a lot of that solvent. In reverse osmosis, this process is basically, well, reversed. A reverse osmosis machine uses a semi-permeable membrane as a filter and it also uses a lot of pressure, more pressure than the normal process of osmosis creates. The product, RO water, is free of any impurities that might have been present before it went through the machine. People use these machines to make sea water safe to drink, by removing all the salt. They also use them to purify water that is going to be used in very sensitive environments, such as coral tanks or other marine tanks.