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National Drinking Water Database


National Drinking Water Database - Get a Filter

EWG's water filter buying guide


Use this guide to choose the right filter for removing the pollutants in your tap water. Already know what you want? See all water filters.

 

Step 1. Decide what is most important to you.

Just want a decent filter at a decent price?Get a carbon filter. (Pitchers, faucet mounts, and large dispensers are popular types. Effectiveness varies widely.)
Want to remove as many contaminants as possible?Use reverse osmosis (RO) combined with a superior carbon filter. (Note - many brands use only minimally effective carbon filters.)
Need to fix a water hardness issue? Use an ion exchange filter to soften your water.
Interested in removing a specific contaminant?Keep reading.

 

Step 2: Consider what style of water filter would work best for you.

StyleProsCons
Pitcher/Large dispenserPitchers or large dispensers are typically fitted with an activated carbon filter that can remove contaminants and improve taste and odor. Models vary, but many reduce chlorine, lead, mercury and (less frequently) disinfection byproducts. This filter style works well for filtering drinking water and can be stored in the refrigerator.Inexpensive. No installation required. Available in various sizes and styles.If filters are replaced regularly, yearly cost may equal expense of faucet, countertop or under-sink filters. Can require frequent filter changes. Filtering is slow.
Faucet mountedFaucet-mounted filters attach directly to the end of the faucet. Most can be pivoted to an “on” or “off” position, allowing you to collect filtered water for drinking and cooking. This filter style typically uses an activated carbon filter that can remove contaminants and improve taste and odor. Models vary, but many reduce chlorine, lead, mercury and (less frequently) disinfection byproducts.Relatively inexpensive. Easy to install. Allows user to switch between filtered and unfiltered water. Filtration is fast enough to fill cooking pots. Does not work with all faucet styles. May slow down faucet flow rate. Typically must change filter more frequently than with countertop or under-sink filters.
Faucet integratedFaucet-integrated filters are either built into the faucet spout, or are housed under the sink. This filter style typically uses an activated carbon or ceramic filter. Models vary, but many reduce chlorine, lead, mercury, and (less frequently) disinfection byproducts.Often allows user to switch between filtered and unfiltered water very easily. Ideal for both drinking and cooking water. Requires installation and possible plumbing modification. Often expensive. Relatively new products, not much consumer feedback available.
On-counterOn-Counter filters typically sit on the counter, with a line connecting directly to the faucet. A diverter value allows you to switch between filtered and unfiltered water. You collect filtered water from an extra spout or faucet on the filter unit. Models use a range of technologies, including activated carbon and reverse osmosis. Effectiveness varies widely between models, but many on-counter filters will reduce a wide array of contaminants.May allow user to switch between filtered and unfiltered water. Typically requires relatively infrequent filter changes. Ideal for filtering both drinking and cooking water.Requires installation and possibly plumbing modification. Can be expensive, though not always.
Under-sinkUnder-Sink filters are mounted underneath the kitchen sink, where they are fitted to the water supply line. Some models have a separate spout or faucet for water collection. Models use a range of technologies, including activated carbon to reverse osmosis. Effectiveness varies widely between models, but many under-sink filters will reduce a wide array of contaminants.Placed out-of-sight under the sink. Typically requires filter changes relatively infrequently. Ideal for filtering both drinking and cooking water.Requires installation and possible plumbing modification. Can be expensive, though not always.
Whole houseWhole House filters screen water as it enters the house, filtering water for a wide range of household uses including drinking, cooking, and bathing. Some models are designed to be water softeners, reducing levels of calcium and magnesium. Others are fitted with mechanical and/or carbon filters to reduce rust, sediment, and some contaminants. Since these types of filters vary more than most in terms of effectiveness, EWG recommends that you contact the manufacturer to learn which filter is best for your needs.Filters all water, including for tooth-brushing, showering, and other uses missed by a kitchen filter.Some are designed to remove a limited number of contaminants, such as sediment and rust. (Others remove a wider range, including volatile organic compounds.) Filters with the highest pollutant removal rates clog faster and reduce water flow.

Step 3: Determine what contaminants you need to remove.

You may already know what chemical pollutants you want to be sure your water filter removes. But if you don't, a great place to start is to look at what kinds of contaminants are showing up in your community's drinking water. Look up your water system on EWG's tap water database. Can't find your system? Call your local water utility and ask them to send you a copy of their Consumer Confidence Report, which contains information on its testing of your system's water.

Not all water filters are created equal, and you may not be able to trust companies' marketing claims. To help consumers find one that best fits their needs, EWG has created an on-line guide to filters certified by the California Department of Public Health for effectively removing key contaminants.

Step 4: Find a filter that works for:

System type
Filter technology
Certified to remove
see more contaminants

 

The Nitty Gritty on Filter Technologies

Although there are hundreds of brands of home water filters, they all rely on a small number of technologies to remove contaminants, That does not mean that every filter using a given technology is as good as another, but it does mean that you can get a good idea of the general pros and cons of the different systems relatively easily.

A few tips to keep in mind when looking at filters:

  • Some filters use a combination of technologies, while others rely on just one.
  • To ensure that a filter removes a particular contaminant, verify that it is certified by a reputable, independent agency for that contaminant. For example, some carbon filters can remove chloramine but others can't. Filters vary widely in quality.
  • If a filter is labeled "NSF certified," it may be certified by this product evaluation company to improve water's taste and odor but not necessarily guaranteed to remove any specific contaminants. Read the fine print.

The basics of common water filter technologies

Carbon/Activated Carbon: Activated carbon chemically bonds with and removes some contaminants in water filtered through it. Carbon filters vary greatly in effectiveness: some just remove chlorine and improve taste and odor, while others remove a wide range of contaminants including asbestos, lead, mercury and VOCs. However, activated carbon cannot effectively remove other common "inorganic" pollutants such as arsenic, fluoride, hexavalent chromium, nitrate and perchlorate. These filters come in two forms, carbon block and granulated activated carbon.

Carbon Block: Carbon block filters contain pulverized activated carbon shaped into blocks under high pressure. They are typically more effective than granulated activated carbon filters because they have more surface area of activated carbon. Their effectiveness depends in part on how quickly water flows through. A proprietary form called "Fibredyne block" claims to have a higher sediment holding capacity and than relative to other carbon block filters.

Granulated Activated Carbon: These filters contain fine grains of activated carbon. They are typically less effective than carbon block filters because of their smaller surface area. Effectiveness also depends how quickly water flows through.

Ceramic: Ceramic filters have with very small holes throughout the material that block solid contaminants such as cysts and sediments from passing through. They do not remove chemical contaminants.

Deionization: An ion exchange process removes mineral salts and other electrically charged molecules from water. The process cannot remove non-ionic contaminants (including disinfection byproducts and other common volatile organic compounds) or microorganisms.

Ion Exchange: This technology passes water over a resin that replaces undesirable ions (charged particles) with others that are more desirable. One common application is water softening, replacing calcium and magnesium with sodium. The resin must be periodically "recharged" with replacement ions. Ion exchange filters are occasionally combined with other types of filters and are used in water softeners, described below.

Mechanical Filters: Like ceramic filters, these filters are riddled with small holes that remove contaminants such as cysts and sediments from water. They are often used in conjunction with other kinds of technologies, but sometimes are used alone. They cannot remove chemical contaminants.

Ozone: Ozone kills bacteria and other microorganisms and is often used in conjunction with other filtering technologies. It is not effective in reducing levels of chemical contaminants.

Reverse Osmosis: This process relies on a semi-permeable membrane that retains particles larger than water molecules. Reverse osmosis can remove many contaminants not removed by carbon, including arsenic, fluoride, hexavalent chromium, nitrates and perchlorate. Quality varies, both in terms of the membrane system itself and the carbon filter typically used with it. The filters use 3 times to 20 times more water than they produce, so they are usually used only for drinking and cooking water.

UV (ultraviolet): These systems use ultraviolet light to kill bacteria and other microorganisms. They cannot remove chemical contaminants.

Water Softeners: These devices use ion exchange to lower levels of calcium and magnesium (which can build up in plumbing and fixtures) as well barium and certain forms of radium. They do not remove most other contaminants. Since water softeners usually replace calcium and magnesium with sodium, treated water typically has high sodium content. Some people may be advised by their physicians to avoid softened water. It is also not recommended for watering plants and gardens for the same reason.

Notes

California certification: If a drinking water device makes a claim about reducing the levels of certain toxic chemicals (or makes any other health-related performance claims), this device must be certified by the California Department of Public Health (CDPH) as being able to live up to these claims in order to be sold in California. CDPH does not, however, regulate claims that are purely aesthetic.

NSF certification: The National Sanitation Foundation (NSF) is a third-party testing organization that certifies drinking water treatment devices for their ability to meet certain standards of contaminant removal. These contaminants may be related to health concerns (i.e. toxic chemicals) and/or aesthetics (i.e. chlorine content or water hardness).