What the best water filter has

  • Large water capacity. The most useful pitcher filters are a compromise between your water use and your available space. Although larger water filter pitchers and dispensers take up more room in the refrigerator, the extra capacity may be necessary to meet your household's drinking-water needs.
  • The ability to remove a high percentage of contaminants. Most water filters use carbon, which absorbs impurities and odor as the water passes through the porous material. Multistage filters can remove contaminants such as lead, chlorine, parasites, pharmaceuticals, bacteria and harmful chemicals, and the semi-permeable membranes of reverse osmosis systems flush the highest percentage of contaminants away with waste water.
  • A moderate to fast flow rate. Most water filters will noticeably slow your flow rate, but a unit becomes inconvenient if it takes too long. Standard flow speed varies depending on the type of water filter. You can find out the gallon-per-minute output of certified filters on the NSF International website.
  • Certifications backing up contaminant removal claims. Manufacturers may test their own products, but a water filter isn't certified to remove contaminants unless it has been tested by an independent organization like NSF International or the Water Quality Association. Both have databases that consumers can easily search to learn more about the features of specific models.
  • A filter change indicator. Typically, these don't test the water to see when a filter should be replaced. A good unit includes an indicator that measures how much water it has filtered. Less accurate indicators are only timers that count the number of months the filter has been in service.
  • Compatible attachments. For installed filters, the best systems are compatible with a wide range of faucets, sinks and plumbing. Occasionally, consumers may need to purchase additional connections or accessories like extension hoses to make a filter more usable.
  • Long warranty. A 90-day warranty may be suitable for a pitcher filter, but a longer warranty of one or two years is best for any filter that requires installation.

Know before you go

What contaminants affect your drinking water? Not all water is the same, and it's important to know what contaminants are present in the drinking water in your area. This will help you determine whether you need only a basic filter to improve taste or a sophisticated system that reduces pollutants and parasites. More information on your local water supply and how to find a state-certified tester can be found at the United States Environmental Protection Agency website. Once you pinpoint your specific water concerns, you can identify the best water filters for your needs.

How much water do you want to filter? If problems like sediment or sulfur are severe, you may want to consider a whole-house filter, although these won't remove all contaminants. If you need filtered water just for drinking, a pitcher may suffice. Cooks will find faucet-mount and under-sink filters more convenient as they won't need to continuously refill a carafe.

What color options do you prefer? Most faucet-mount filters come in only one or two colors, while pitcher filters are available in a large range of colors and styles. Spouts for under-sink units typically come in one finish, but users can buy aftermarket replacements to better match their kitchen faucet.

Do you want recyclable filter cartridges? Consumers who want to reduce their consumption of bottled water because of the environmental impact may want to buy a brand of water filter that offers a recycling program since filters must be replaced as often as every month. Brita filters, for example, can be dropped off at Whole Foods Market locations or mailed to Preserve, the company handling Brita's filter recycling.

How permanent do you want the water filter to be? Pitcher or faucet-mounted water filters are likely the best option for dorm residents or renters who can't make permanent modifications to their living spaces. Under-sink water filters may require a certain level of expertise to install, which may necessitate paying a professional to do it.

Value expectations: the dollars and cents of it

Consider annual cost and maintenance requirements. Water-filtering pitchers and faucet-mounted filters aren't that expensive, but the cost of replacement filters will quickly outpace the initial purchase price. Use the cost of replacement filters and manufacturer recommendations on filter life to estimate your annual expenses. Cleaning, battery replacement and new semi-permeable membranes are additional charges for reverse osmosis systems. Also, consider the cost of discarded waste water if your supply is limited or you have high municipal water rates.

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