Reverse osmosis is water pushed through a multi layered membrane. Each layer has smaller and smaller holes. Once the water reaches the center there's really nothing left but h2o. As a matter of fact I have heard of processes that filter the water down to just higrogen and oxegen molecules leaving nothing but pure water. They use it to desalinate water from the ocean in attemps to fix the ever growing proplem of water shortage.
You can buy RO
water from wall mart. Around here its 73 cents a gal
. Other then that you have to get an RO
filter for your sink. I'm not sure if that's what you ment with your question but there it is.