Illustration by Christoph Niemann
If you lived on a deserted island, would you buy a home security system? Consumers do the aquatic equivalent every day, purchasing water filters without knowing if there's anything worrisome in their water. So always test your water first.
If your tap gets a clean bill, save your money, or invest only in a taste-improving carbon filter. If the test reveals sediments, organic (pesticides) or inorganic (lead, mercury) compounds, or microbes, you'll want more scrubbing power-or even a whole-house system, which we're not covering here. Keep in mind that some products combine filtration methods, and always remember to check for NSF certification.
CARBON FILTER
Price: $25
How It Works: Contaminants are trapped as water flows through
Removes: Tastes and odors from organic compounds, plus chlorine and pesticides. Some eliminate heavy metals
Ignores: Microbes and some metals
Product Types: At the tap, carafes, or under sink
REVERSE OSMOSIS FILTER
Price: $200
How It Works: Pressurized water flows across a semi-permeable membrane; water molecules get through, larger contaminants don't
Removes: Most inorganic compounds
Ignores: Microbes and organic compounds
Product Type: Under sink
DISTILLATION FILTER
Price: $150
How It Works: Water is evaporated and condensed with a cooling coil
Removes: Most microbes and inorganic compounds
Ignores: Organic compounds
Product Type: Countertop machine with storage tank
OZONE FILTER
Price: $300
How It Works: The extra oxygen molecule in ozone attaches to contaminants, rendering them harmless
Removes: Most microbes and organic compounds
Ignores: Inorganic compounds
Product type: Countertop machine with storage tank
ULTRAVIOLET FILTER
Price: $160
How It Works: Radiation kills living cells in the water
Removes: Most microbes
Ignores: Inorganic and organic compounds
Product type: Countertop or under sink
SEDIMENT FILTER
Price: $40
How It Works: Contaminants are trapped as water flows through
Removes: Large particles
Ignores: Microbes, organic compounds, and inorganic compounds
Product type: Under sink
HOME TEST KITS
The Golden Rule: Know Your Enemy
There's no substitute for a full-spectrum analysis of your tap water, which screens for 100 contaminants and costs a few hundred dollars. But home test kits are a great way to start-they'll give you a general idea of your water quality in about 10 minutes (you can always follow up with a more extensive test). Look for a kit that checks for EPA-regulated contaminants, like Silver Lake Research's WaterSafe Drinking Water Test ($17, above left), which tests for bacteria, lead, pesticides, chlorine, and more. We also advise that you screen for arsenic.
