The Reverse Osmosis (RO) system consists of several stages of filtration as well as a special membrane that cleans the water thoroughly. Although some RO systems can include up to seven stages of filtration, most have three to five. First, water is sent through a pre-filtration component designed to remove larger particles like dust, rust, and chlorine. These components are usually carbon or sediment filters. Once the water has been filtered, the RO system pushes it through a membrane that allows water molecules to pass through but not contaminants. This stage removes dissolved particles that are too small to be seen even by a microscope. The water is then collected in a storage tank until it’s full—the filtration will then shut off. When you turn the faucet, it goes through one last post-filtration component to completely purify it before drinking.