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.


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


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


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


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


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


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


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.