Whirlpool Gold WHER25

A reverse-osmosis filter is the only good way to eliminate unusual contaminants like nitrates or perchlorate, experts say. However, not many homes need this level of filtration, say most critics. The Whirlpool Gold WHER25 reverse-osmosis filter is less expensive than other models, and it performs almost as well as more expensive systems in comparison tests. The problem is, while reverse-osmosis filters remove almost all contaminants, they also filter out "good" minerals such as fluoride or calcium; plus, the process wastes about five gallons of regular water for every gallon of purified water produced, and flushes contaminants back into the water supply. If you have normal water-contaminant issues, you'll be better off with a filtering pitcher like the PUR CR-600 2-Stage Pitcher (*est. $17) or Culligan US-EZ-4 Under-Sink Filter (*est. $80).

Far and away the most reliable review of the Whirlpool Gold WHER25 reverse-osmosis water filter is by Consumer Reports, which tests this unit against others of its kind and reports on the results.