•  Distillation Units •  Faucet Filters •  Fitness & Nutrition •  Is Your Water Safe? •  Pour-Through Carafes •  Water Safety

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.

Reverse-osmosis filtering is a good choice if you're concerned about a wide range of contaminants -- especially chemicals and heavy metals like lead -- and want the convenience and extra ressurance of drawing triple-filtered water directly from the tap.

A complete system, including a prefilter and a postfilter, strips out lead, copper, arsenic, cadmium, chlorine, giardia, pesticides, salt, trihalomethanes, sulfates, cysts, and nitrates.

The reverse-osmosis membrane can also screen out at least some bacteria and viruses. But because it may contain tiny imperfections that allow a few microbes to slip through, you shouldn't use the filter for protection against these critters.

A reverse-osmosis system offers these advantages: It creates a three-tiered barrier that few contaminants can penetrate, and it uses no electricity. Its main disadvantage is that it wastes two to four gallons of tap water for every gallon that gets filtered. The less reject water it generates, the shorter the life span of the membrane will be, because reject water helps keep the membrane clean.

Unless you're a do-it-yourselfer and like to spend two hours at a time with your head under the sink, call a plumber.

Prices start at under $200 for the system itself. Also, every three to five years you'll need to replace the membrane. The cost of filtered water is around 7 cents per gallon.

Further Resources

The Water Quality Association Consumer Affairs Department P.O. Box 606 Lisle, IL 60532 Phone: 630-505-0160

http://www.wqa.org

References

First published March 3, 1999
Last updated November 15, 2007
Copyright © 1999 Consumer Health Interactive

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