Choosing Home Water Filters & Other Water Treatment Systems

You might be surprised to learn that the main function of popular refrigerator and pitcher filters is to improve the taste of your water, and most don’t fully protect against germs and many other contaminants.

Some people do not like the taste of their tap water. Sometimes this is because of the disinfectant (like chlorine) that helps keep the water safe from germs. Sometimes minerals or other naturally occurring contaminants like sulfur-containing compounds that are not harmful change the taste of the water. Activated carbon filters (the type of filter found in many refrigerators and pitcher filters) can help reduce unpleasant tastes and odors. Reverse osmosis systems can also improve taste and also reduce the levels of common chemicals such as lead. Check the label to ensure that taste and odor (NSF 42) are addressed by the particular filter you are considering. Keep in mind that if you use a chlorine-removing whole-house filter, you might end up increasing the amount of germs that grow in your plumbing.

Most harmful contaminants can’t be seen, smelled, or tasted. Some harmful contaminants, like volatile organic compounds (VOCs)[PDF - 2 pages] that sometimes contaminate private wells, can give water a bad taste and might smell like gasoline or other chemicals. There are many different kinds of VOCs, and they have different health effects: Some cause cancer, irritate skin, affect mucous membranes, or damage the nervous system, liver, or kidneys. To identify the best filter, special testing may be needed to determine which VOCs are present in your water. It is best to use a point-of-entry filter system (where your water pipe enters your house), or whole-house filter system, for VOCs because they provide safe water for bathing and cleaning, as well as for cooking and drinking. Activated carbon filters can remove some VOCs.

If you have a private well and notice a change in the taste of your water, consider having your well water tested. If you have a public water system and notice a change in the taste of your water, report this to your water company. Just keep in mind that the taste and smell (or lack thereof) of water is not necessarily an indication of how free it is from germs and chemicals.

More Information

• USGS. Volatile Organic Compounds in the Nation’s Drinking-Water Supply Wells—What Findings May Mean to Human Health [PDF - 4 pages]
• EPA. Point-of-Use or Point-of-Entry Treatment Options for Small Drinking Water Systems [PDF - 132 pages]

Lead in drinking water often comes from the pipes, and may be a particular concern if children live in your household. If annual water testing of your public or private water source reveals that levels of lead in your water are at or above 15 ppb (parts per billion), there are actions you can take.

• Flush cold water through the pipes by letting the water run before using it—especially if the water has been sitting still for 6 or more hours. If you have lead service lines leading into your home, additional flushing will be needed.
• Avoid using hot water from the tap or boiling tap water.
• Look for a filter that is certified to reduce lead, and maintain it exactly as indicated by the manufacturer.

While these steps may not remove all lead from your water, they may lessen the amount of lead to a safer level for use and consumption.

More Information

• CDC. Lead
• EPA. Actions You Can Take to Reduce Lead in Drinking Water

Arsenic is a heavy metal that is often found in ground water sources, including some private wells and some public water systems that use groundwater. Arsenic is associated with several health problems and can cause cancer.

Arsenic can be present in two forms: trivalent and pentavalent. It is important to know what kind (or "species") of arsenic is present in your water in order to select the best filter. If your water is treated with chlorine, you are more likely to have pentavalent arsenic, which can be removed by filters labeled with the NSF standard 53 or 58. If your water is not treated, additional treatment (a "pre-oxidation step") might be needed to convert the trivalent arsenic to pentavalent arsenic before the water is filtered. Distillation is highly effective at removing arsenic, although this technology is not as practical for home use because it uses more energy and takes longer than other water treatments.

More Information

• CDC. Arsenic
• CDC. Arsenic and Drinking Water from Private Wells
• EPA. Arsenic in Drinking Water
• NSF. Arsenic [PDF - 1 page]

Nitrates are chemicals that get into groundwater from contamination with fertilizer, manure, or septic systems, sewage, or erosion of natural deposits. Nitrates make it hard for your red blood cells to carry oxygen. This can be dangerous for infants and some adults. If you get your water from a public water system, nitrate levels are monitored and controlled. If you have a private well, you need to have your well water tested to find out if nitrates are a problem for you. If testing determines your water has high levels of nitrates, you can choose reverse osmosis (NSF 58) or distillation (NSF 62) technology. Boiling and filtration do not remove nitrates.

If your water contains high levels of nitrates, other contaminants might also be present. Contact your local health department for recommendations about testing for other contaminants.

More Information

• CDC. Nitrates and Nitrites
• EPA. Frequently Asked Questions About Nitrate and Drinking Water [PDF - 2 pages]
• EPA. Drinking Water Contaminants

People who are immunocompromised, or have immune systems weakened by chemotherapy, AIDS, or organ transplants, should consult with their health care provider to determine whether they should consider installing a water treatment system to ensure their water has a low concentration of germs, especially the germ Cryptosporidium. Filters that have the words "reverse osmosis" on the label protect against Cryptosporidium, as do those with an "absolute 1 micron" pore size. You can also look for the standards NSF 53 or NSF 58 on the label.

Cryptosporidium is a special concern for people with compromised immune systems.

Filters designed to remove Crypto (any of the four messages below on a package label indicate that the filter should be able to remove Crypto):

• Reverse osmosis (with or without NSF testing)
• Absolute pore size of 1 micron or smaller (with or without NSF testing)
• Tested and certified by NSF Standard 53 or NSF Standard 58 for cyst removal
• Tested and certified by NSF Standard 53 or NSF Standard 58 for cyst reduction

Filters labeled only with these words may NOT be designed to remove Crypto:

• Nominal pore size of 1 micron or smaller
• One micron filter
• Effective against Giardia
• Effective against parasites
• Carbon filter
• Water purifier
• EPA approved Caution: EPA does not approve or test filters
• EPA registered Caution: EPA does not register filters based on their ability to remove Cryptosporidium
  
• Activated carbon
• Removes chlorine
• Ultraviolet light
• Pentiodide resins
• Water softener
• Chlorinated
  

In addition, immunocompromised people should not change water filters themselves, as this may expose them to the contaminants collected by the filter and potentially increase their risk of infection.

Some filters can remove parasites such as Cryptosporidium and Giardia if used properly. However, they may not remove viruses and bacteria. Germs could still be present in your filtered water.

There are a range of water treatment options that campers and travelers may consider if they anticipate having access to mainly untreated or poorly treated water sources. Boiling water is the most effective approach to killing all kinds of germs in water. Using an absolute 1-micron filter (1-micron sized holes or smaller) or a filter labeled as certified by NSF Standards 53 or 58 will remove parasites if used properly, but will not remove viruses or all bacteria. Check the label of your filter product.

If you are making a solution for irrigating, flushing, or rinsing your sinuses (for example, by using a neti pot, sinus rinse bottle, or other irrigation device), or putting water into the nose as part of a religious practice, use safe water to lower your risk of infection with Naegleria fowleri. This tiny ameba causes a rare infection by traveling up the nose to the brain and causing death.

Take at least one of these actions to lower your risk of becoming infected:

• Boil: Use water that has been previously boiled for 1 minute and left to cool.
  • At elevations above 6,500 feet, boil for 3 minutes.
• Filter: Use a filter designed to remove some water-loving germs.
  • The label may read "NSF 53" or "NSF 58."
  • Filter labels that read “absolute pore size of 1 micron or smaller” are also effective.
• Buy: Use water with a label specifying that it contains distilled or sterile water.
• Disinfect: Learn how to disinfect your water to ensure it is safe from Naegleria.
  • Chlorine bleach used at the right level and time will work as a disinfectant against this germ.

Hard water, or water that contains excessive amounts of minerals like calcium and magnesium, can leave a scaly residue and prevent soaps from lathering. Water softeners can be used to treat this problem. Water softeners use ion exchange technology, so they are technically not filters and do not protect you from germs in the water. Water softeners also remove beneficial minerals from the water.

More Information

• USGS. Water Hardness and Alkalinity
• American Water Works Association (AWWA). Facts and Filters: Water Softeners [PDF - 2 pages]