Hello Neww, I am curious how I got asked this question as I first entered BlurtIt to find help to fix my washing machine. But to answer your question, water on earth is naturally purified when it evaporates into the atmosphere. When water evaporates, it is "distilled" into water vapor, and impurities are left behind. This includes salt from sea water, minerals from the ground, or pollutants. When the water vapor forms clouds, then condenses into rain or snow, the pure water falls back to earth. Water is also "cleaned" as it passes through plants or seeps through rock layers. Randarr