Reverse Osmosis water filter systems are good at removing most contaminants from water sources but the Reverse Osmosis system cannot remove things such as pesticides, solvents and volatile organic chemicals (VOCs) including: Ions and metals such as Chlorine and even Radon.
Reverse Osmosis water filter systems can remove things such as dissolved salts, Lead, Mercury, Calcium, Iron, Asbestos and Cysts.