What is a reverse-osmosis water filter?
A complete reverse-osmosis filter system is an under-the-sink obstacle course, stopping nearly every contaminant that tries to take a ride up your cold-water line. Models vary somewhat, but most units force water first through a flashlight-size “prefilter” that strains out sediment and then through a cellophanelike membrane that screens out even smaller pollutants. Before reaching a special faucet mounted on your sink, the now-clean water gets one last scrubbing from a carbon filter that removes any lingering chemicals picked up along the way.
