Most drinking water in the U.S. is safe. But if you have any qualms about the quality of your tap water--or simply don't like its taste or smell--you may want to consider getting a water filter. While boiling your tap water can protect against some organisms, it won't remove lead or stable organic compounds that can affect its taste.

Facts about your water supply can help you decide. A federal law requires water utilities serving more than 10,000 people to send an annual report to their customers that clearly explains exactly what's in the water when it leaves the treatment plant. Some states have required such reports for years. If your water utility serves 10,000 or fewer, you may find information at a public library or in a local newspaper. People with a well or on a very small system must have testing done on their own.

What's available

The major water-filter brands are Brita, Culligan, Kenmore (Sears), Omni, Pur, and Teledyne/Water Pik. There are several types of filters, some less expensive to maintain than others.

Carafes. Generally made of plastic, these are simple to use and typically come in a half-gallon size or larger. Many can fit in the door of a fridge. Filter changes are usually required after processing 40 gallons--the equivalent of about three months of typical use.

Price range: half-gallon size, $10 to $40. Annual filter cost: $25 to $80.

Faucet-mounted filters. Models that attach to your faucet are compact and easy to install. The filter should generally be changed after processing 100 to 200 gallons--at least every three months or so.

Price range: $15 to $40. Annual filter cost: $45 to $90.

Faucets with built-in filters. Some faucets are sold with filters, though these are a relatively expensive option if you don't need a new faucet. Faucets with built-in filters didn't perform as well as the faucet-mount filters or most of the carafes in our tests. Filter-change intervals are as for faucet-mounted filters.

Price range: $150 to $300 for the faucet. Annual filter cost: $40 to $95.

Refrigerator filters. You'll find two types. Built-in models are sold as a step-up feature with some refrigerators, while add-on units must be installed (often by a plumber) in the tubing that supplies water to a refrigerator. Both typically require filter changes after processing 250 to 400 gallons, or at least twice yearly.

Price range: add-on, $20 to $40. Annual filter cost for add-on, $5 to $20; built-in, $60 to $90.

Other options. Countertop filters often rely on a single filter cartridge.

Price range: $40 to $300. Annual filter cost: $10 to $125.

Under-the-sink filters use one to three filter cartridges.

Price range: $40 to $500. Annual filter cost: $10 to $200.

Whole-house systems can be as simple as an in-line single-stage filter or as elaborate as a large carbon cylinder. Price range: $40 to $1,000. Annual cost: $100 to $175.

For all of these types, follow manufacturers' instructions regarding how often filters should be changed.

Some contaminants require special filters to remove them. You may need a plumber to install a reverse-osmosis system, typically under the kitchen sink. It combines conventional filters with a reverse-osmosis unit--a special cellophanelike membrane that removes many contaminants, including industrial chemicals, lead, nitrates, and toxic metals such as barium and chromium. Remember, however, that smaller reverse-osmosis models can produce only a few gallons of filtered water per day.

Price range: $200 to $1,000. Annual filter cost: $100 to $175.

Follow manufacturers' instructions regarding how often filters should be changed.

Important features

Many carafe and faucet-mounted filters have a flashing light, color indicator, or other device signaling the need for a new filter cartridge. We've found that most such signals aren't particularly accurate, although slower-than-usual water flow may tell you that it's time to replace the cartridge, since flow tends to slow or stop as impurities collect in the filter. Faucet-mounted filters allow you to choose unfiltered water for cleaning or washing.

Faucets with a built-in filter didn't perform as well in Consumer Reports tests as the faucet-mounted filters or most of the carafes. Refrigerator filters fell short of the faucet-mounted units and the carafes. Most claim only taste and odor removal. Under-the-sink filters didn't necessarily filter more effectively than countertop units. The best reverse-osmosis systems earned top scores across the board in our previous tests. But most people don't need that degree of filtration. What's more, these filters tend to produce a relatively limited supply of filtered water.

Recommendations. Consider your daily water use to help determine the filtering equipment you need. A carafe filter or a faucet-mounted filter might be fine if you need to filter only a relatively small amount of water each day. Also determine how often you'll have to change filters, which affects annual costs; follow the manufacturer's recommended replacement schedule, since bacteria can thrive inside a filter. Also consider the type and degree of contamination; if, for example, the water has a high level of certain chemicals such as trihalomethanes, you may also need a separate shower filter.

Finally, if you decide that your water does need filtering, don't stop with the filter. Compare notes with neighbors and notify the water utility and local health officials, who can help locate the problem and eliminate it at its source.