Contaminant removal varies even within type. All filters are designed to be used with cold water only.
Carafe
Best for filtering small quantities of drinking water inexpensively without the hassle of installation. But some are slow, prone to clogging, and have a short filter lifetime. Price $15 to $60.		Illustrations by Trevor Johnston
Faucet-mounted
Best for filtering drinking and cooking water with minimal installation effort. Also allows easy switching between filtered and unfiltered water. But slows the flow of water and can’t be used on all faucets. Price $20 to $60.
Countertop
Best for for filtering large quantities of water without plumbing modification. Less likely to clog than carafes or faucet mounts. But can clutter countertops and can’t be used on all faucets. Price $50 to $300.
Undersink
Best for filtering lots of water without modifying the existing faucet or cluttering the counter. But takes up cabinet space and requires plumbing modifications. A hole must be drilled through the sink and/or countertop for the dispenser. Price $55 to $350.
Reverse-osmosis
Best for removing a wide range of contaminants, including dissolved solids, and is the only filter certified to remove arsenic. But requires plumbing modifications and must be periodically sanitized with bleach. Is extremely slow and creates 3 to 5 gallons of waste water for every gallon filtered. Takes up cabinet space. Price $160 to $450.
Whole-house
Best for inexpensively removing sediment, rust, and for some, chlorine, from household water. Long cartridge lifetime. But most not designed to, and won’t effectively remove, most other contaminants, including cysts, metals, and VOCs. Whole-house systems require professional installation. Price $35 to $80.

Features that count

Several undersink and reverse-osmosis models use simple screw-on plumbing connections instead of saddle valves, which require drilling into the cold-water supply line and can leak. More filters feature electronic indicators, which show when it’s time for filter replacement. Also look for an electronic touchpad.