Drink cleaner, refreshing water with the PUR 3-Stage Quick-Connect Reverse Osmosis (RO) Water Filtration System. Conveniently install this 3-stage RO water filter system under your sink to deliver more purified water through a secondary air gap faucet. Make an environmental choice and avoid bottled water, choosing this water filtration system that is NSF certified to reduce at least 15 unwanted contaminants including lead, cysts, TDS and heavy metals. During stage 1, the 5 micron carbon block filter reduces particulates and chlorine. In stage 2, the RO membrane further filters to less than 0.0001 micron, thereby reducing chemical contaminants and improving the safety of your drinking water. In the final 3rd stage, a secondary carbon block filter removes any residual taste that may come from the storage tank. This quick-connect design makes replacing the filters a breeze with a simple flip of a switch and twist of the wrist. For best water filtration system maintenance, replace the carbon block filters every six months and the RO membrane every two years. This water filtration system features a compact, bracket-mounted space-saving design with everything you need for quick and easy installation.