I have RO I use for drinking water and cooking. Any more than that is impractical and cost prohibitive. The world is polluted. Might be able to get away from most of it by living in a cabin in the woods. But then again all the wild life piss and shit also flows downhill. And that natural spring might just be chalk full of arsenic, asbestos, mercury, lead, etc. Bottom line there is no escaping contaminants. Do what you can within reason.