The PuROTwist PT4000T36-GOLD Reverse Osmosis System has a standard certification of NSF/ANSI 58 Gold Seal by Water Quality Association, America. It has 4 stage filtration process that can give you extra pure drinking water. It has 5 micron sediment filters that can separate up to 85% of particles. Sediments can decreases the level of taste in your beverages, so a sediment filter will remove that. Sediment filters are judged on the basis of micron members and this one exactly fit the standard. At the second stage, it has a per-carbon filter that can protect the RO cartridges from chlorine. In the stage 3, the cartridges will eliminate dissolved inorganic particles from the water including salt and others. The stage 4 includes a post carbon filter that will enhance the taste of drinking water.