Under-sink water filters are installed directly into the water line and clean all cold water that flows through the faucet. Ideal for filtering both drinking and cooking water, this system doesn't require switching the filter on and off. Because it's hidden out of view, it doesn't encroach on countertop or sink workspaces.
Prices and options range dramatically. Upkeep is far less than pitcher or faucet filters, with maintenance required about twice a year. Annual costs for maintenance and replacement filters also vary widely, and this is important to consider when purchasing an under-sink filter.
Water sources with excessive sediment or pollutants may require a reverse osmosis system. These are permanently plumbed into the kitchen freshwater and sewer lines, with a separate spout for water delivery. Costs vary from a few hundred dollars to almost $2,000, but you don't have to spend top dollar for a quality unit.
The Whirlpool Reverse Osmosis Filtration System WHER25 (*Est. $155) is a great budget option. Experts say it has outstanding filtering -- it removes 90 percent of dissolved solids -- but comes with basic features. Many users on Lowes.com and Amazon.com have no problems following the step-by-step installation instructions and video. If you lack basic plumbing knowledge or tools, you may need to hire a professional to install the unit.
Users say the 3M Filtrete Under-Sink Advanced Water Filtration System (*Est. $37) is the best basic under-sink filter. It improves taste by reducing chlorine and odors, and is certified to reduce cysts. Numerous owners who post comments at Amazon.com and Lowes.com say it's easy to install and doesn't leak, although it does reduce cold water flow to 1.5 gallons per minute. On Amazon.com, one owner says it takes 10 minutes to install and delivers great-tasting water, adding, "My wife and I both are highly impressed with this filter."