Water Filter Buying Guide

We test water filter pitchers by timing how long it takes the pitcher to finish filtering 1 quart of water at multiple intervals until we’ve gone through as much as 40 gallons of water, which is the typical lifespan of this type of water filter. We also measure whether a filter’s flow rate slows down (gets clogged) over the course of the cartridge’s capacity and, if so, by how much.

If a manufacturer claims that a pitcher meets NSF/ANSI standards for removing specific contaminants, such as chlorine and lead, we verify each claim. NSF International and the American National Standards Institute develop filtration standards.

We also check claims of flavor and odor reduction by spiking water with commonly found compounds that can make water smell and taste like a sewage treatment plant, damp soil, metal, or a swimming pool. A trained panel of professional tasters evaluates how successful the filters are at removing these flavors and odors.

The best performing filters work well enough that most people wouldn’t be able to discern a palatable difference between the filtered water and pure spring water. But on the other end of the spectrum, if it does a poor job, you’ll probably be able to taste the difference.

We test under-sink filters by measuring how effectively they remove flavor and odor taints from a CR-created "control water" sample. Then we examine how close that control water compares with regular filtered water. We determine the flow rate by the time it takes to filter 1 quart of water, and clogging reflects whether and how the filter’s flow rate slowed over the course of a cartridge’s lifespan. We also verify under-sink filter claims of lead and chlorine removal.

The Environmental Protection Agency requires community water suppliers to provide a Consumer Confidence Report to customers every July. A CCR states the levels of contaminants detected in the water and how they compare with the EPA’s drinking water standards. If you rent an apartment, contact your building manager or local water company for a copy.

Community water systems providing water to 100,000 or more people must post the reports online. If you’re on well water, you won’t have a CCR because the EPA doesn’t regulate private wells. In that case, check with the Centers for Disease Control and Prevention for information on well testing and treatment.

The water quality report tells you about the water in your municipality, but if your home was built before lead-free pipes were mandated in 1986, a test is the best way to assess the quality of the water coming out of your faucets at home. There’s no safe level of lead exposure, according to the EPA.

In the CR-Guardian study, almost every test sample had measurable levels of PFAS, which are linked to cancer, learning delays in children, and thyroid disease. More than 35 percent exceeded the maximum safety threshold specified by CR scientists and other health experts.

PFAS, found in hundreds of household products, are a growing concern. At least 2,858 communities in all 50 states and two territories have drinking water contaminated with PFAS, according to a June 2022 analysis by the Environmental Working Group, an advocacy organization. Thus far, the EPA hasn’t set an enforceable legal limit for PFAS in drinking water—however, there is now a roadmap stretching into 2024 that will hopefully move PFAS regulation in the right direction.

Your state or local health department might offer free water test kits, and test kits are sold at home improvement stores, where they generally cost $10 to $30, depending on what exactly they test for. The EPA recommends sending samples to a certified lab for analysis. Your local water authority can offer a list of labs. Or you can check the EPA’s list or call the agency’s Safe Drinking Water Hotline at 800-426-4791. For more on testing your water, see our interactive guide.

What a filter removes from water varies. Our water pitcher tests found that all models effectively remove chlorine and four models remove lead. All under-sink filters in CR’s ratings meet the strict standard of lead and chlorine removal. 

Once you know what’s in your tap water, choose a filter that best suits your needs. Look at the filter’s packaging for its contaminant removal certifications, if any. Third-party labs that certify products to NSF standards include the CSA Group, Underwriters Laboratories (UL), and the Water Quality Group (WQA), so you may see those certification seals, too.

All filters must be replaced periodically to function effectively. Check the specs in the full view of our ratings to compare the costs of replacing filters for one year. For example, the pitcher filters we test range from $16 to $150; you’ll also see which models have a filter-life indicator, a handy feature that tells you when it’s time to change the filter.