After more than 20 hours of in-house testing and two independent lab tests we’re confident the Pur Classic 11-Cup (aka Pur LED) is the best water-filter pitcher for most people. At the heart of the matter is the filter itself: The Pur’s filter is certified by the NSF International to significantly reduce 10 contaminants, including several heavy metals and biocides. That’s more contaminants than any other pitcher of its type that we tested.
It also virtually eliminates chlorine (the chief contributor to bad-tasting tap water) and, according to Pur, also reduces levels of 12 pharmaceuticals—an emerging contaminant concern in the water supply—by at least 96 percent. Finally, in our independent lab test the Pur reduced the lead levels in an extremely lead-rich water sample by a remarkable 97 percent. Because the NSF hasn’t certified it for lead removal, we can’t officially state that it does so. But we like those unofficial results.
The Pur also simply produces great-tasting water. Add in its excellent ergonomics, ease of maintenance, wide availability, low upfront cost, and reasonable prices for replacement filters, and you have a winning pitcher.
We also really like the Mavea Elemaris XL, a nine-cup pitcher. Its filter eliminates seven contaminants to NSF standards and in our independent test it reduced lead levels in the same extremely lead-rich sample we used to test the Pur by a decent 73 percent. The Mavea has the best ergonomics of all the pitchers we tested and comes in a range of bright colors—not an option offered by many filter makers. Plus, it makes great-tasting water. Finally, though nearly every filter cartridge out there is recyclable, Mavea uniquely offers both drop boxes and free return-shipping labels so you can ensure that your used filters don’t go to a landfill. Initial and replacement-filter costs are a bit higher than Pur’s, but compared to the rest of our test models, Mavea’s pitcher is still a far better product.
Oh, and before you ask about Brita, the dominant player in the market, both of our recommendations comprehensively outrank it on filtration performance, ergonomics, and ease of maintenance.
Table of contents
- Why you should trust me
- How we picked
- Our pick
- Flaws but not dealbreakers
- A slightly less effective filter
- How we tested
- The competition
- How to find out if your water is safe to drink
- Contaminants that could be in your water
- When to change your filter
Why you should trust me
I have over 20 years of lab and field research experience in physics, chemistry, and earth and atmospheric sciences, including characterizing rainwater samples across the Pacific and Indian Oceans. I’ve developed a new class of lasers at the National Institute of Standards and Technology (NIST), performed rocket science at NOAA, and led research to develop a more comfortable and effective particle respirator using nanotechnology. Working with The Sweethome over the past several years, I’ve done exhaustive, objective analyses of air filters and humidifiers.
How we picked
When we decided to test water filters, we also decided to limit our search to the most affordable, lowest hassle, and (not coincidentally) most popular option: filter pitchers. We’ll likely also test another popular type—under-sink filters that connect directly to the plumbing—at some point as well. But for most people, a filter pitcher is the first option because it’s inexpensive, it’s easy to clean and maintain, and you can take it with you when you move to a new home.
As a rule, we restricted our search to the simplest and most common type of filter pitcher: gravity-fed. The popular Brita pitcher is a familiar example of how the process works: You pour water into a top chamber where it drains via gravity through the filter to a second chamber below. Gravity-fed filters are slow, but they’re easy to use and maintain.
We made one exception to the rule, however, for a well-regarded Clear2O pitcher that employs a hose connected to a faucet to force water through the filter. It’s a fast and effective method, but we found it has serious drawbacks (see The competition, below).
We also focused our search on filter pitchers that the NSF International certified or that have met the NSF’s certification requirements.1 The NSF has two main testing standards that apply to pitcher-style water filters: Standard 42 measures the removal of chlorine taste and odor (municipal water supplies commonly get chlorine added to kill pathogens) and Standard 53 measures the removal of numerous contaminants, including lead, mercury, benzene, and various biocides. The NSF certifies filters for each contaminant individually, not for groups of contaminants, and few if any filters earn certification for everything.
It’s important to note that no filter completely removes all of a contaminant, even those contaminants for which the filter is certified. Certification means that a filter removes a significant percentage of a given contaminant—anywhere from 50 percent to nearly 100 percent—and reduces it to a level considered safe by the EPA. And most filters do not remove the total dissolved solids that characterize mineral-rich “hard water,” so if that’s your aim, you’ll need to find another resource.
Finally, using existing reports (particularly from Consumer Reports and sales data), trustworthy user reviews, and our own experience, we came up with a list of seven pitchers to test, each from a top-selling brand: one apiece from Brita, Mavea, Pur, Soma, and ZeroWater, and two from Clear2O (the faucet-fed model and a gravity-fed model).
For consistency in testing, and because it’s the most popular size, we chose the approximately 10-cup (roughly 2.5-liter) pitcher from each manufacturer. But because manufacturers generally use the same filter cartridge across their whole line of pitchers, you can consider our test results broadly representative.
The Pur Classic removed the largest number of contaminants among all the gravity-fed filters in our test. It also pours neatly, is comfortable to hold, and refills more quickly and easily than others despite the fact that it has the biggest reservoir of any pitcher we tried. Our subjective tasters liked its water’s flavor the best, and it’s one of the cheapest products to own long term.
In our own tests, the Pur virtually eliminated chlorine—the major culprit for bad taste and odor—and reduced lead levels by 97 percent.
The Pur’s NSF-certified filtration system successfully removed a total of 13 contaminants, including chlorine (for odor and taste), cysts (cryptosporidium or giardia), benzene (a common, carcinogenic hydrocarbon), carbon tetrachloride and tetrachloroethylene (common cleaning agents known to cause liver and nerve damage and cancer), three herbicides (2,4-D, atrazine, and simazine), particulate matter, zinc, and copper, mercury, and cadmium (metallic elements that can cause severe health problems). Pur additionally claims (from internal tests) that it reduces 12 waterborne pharmaceuticals by greater than 96 percent. In our own tests, the Pur virtually eliminated chlorine—the major culprit for bad taste and odor—and reduced lead levels by 97 percent in a water sample with 16 times the lead levels used for NSF testing. The American Dental Association also endorses the Pur as not removing fluoride.
Assembling the Pur is straightforward. A tab on the lid aligns with the handle, making it easy to fit into place. To install the filter, you simply align a pair of tabs, drop the filter into its slot, and twist one quarter turn clockwise to secure the filter and form a tight seal with the O-ring.
Filling is easy, with a large 3-inch-diameter flap that opens via a lip at the handle. A filter-status indicator flashes green to indicate the filter is okay, yellow to alert you to replace the filter soon, or red to warn you to replace the filter now. The filter is rated for 40 gallons—the general rate for pitcher filters—which should last you two months. (When you change the filter, reset the indicator by holding it down for five seconds.) Other thoughtful features are a small lip on the lid by the handle to facilitate removal for cleaning, and an unimpeded pour spout without a flap (a flap can make pouring into bottles tricky).
The Pur also has the largest reservoir of all the pitchers we tested (2.6 liters, about 3 quarts or three-quarters of a gallon). And its upper tank (the place the water goes before it drips down into the reservoir) is also the best-in-test in terms of size and efficiency. One fill of the Pur’s tank results in nearly three-quarters of a pitcher of filtered water. Others get you three-fifths of a pitcher, or even half a pitcher, per fill. With the Pur’s more ample upper tank, you’ll make fewer trips to the sink and spend less time waiting for water to finish filtering.
With the Pur’s more ample upper tank, you’ll make fewer trips to the sink and spend less time waiting for water to finish filtering.
The Pur had excellent subjective taste ratings and after spending a week with a kitchen full of pitchers to choose from it was the filter my wife and I found ourselves reaching for most often. The Pur pitcher also has very good ergonomics, including an S-curved handle with a hand-fitting grip.
Finally, as a bonus to the excellent performance and usability, it has the second-lowest cost of ownership—only the not-recommended Brita is cheaper.
Flaws but not dealbreakers
One of the downsides of having the largest capacity is that the pitcher itself is large and can be heavy when full. If you find that to be troublesome, we recommend filling it no more than halfway. Also, it’s still agonizingly slow to filter when you’re thirsty, but that’s an issue with most gravity-fed pitchers. If you top the pitcher off after each use, it isn’t an issue.
In July 2016 we became aware of a problem with the Maxion filter cartridges used in the Pur Classic (our top pick) and other Pur pitchers. Namely, they are prone to “locking up” suddenly and no longer allowing water through—the result of air bubbles getting trapped in the carbon filter particles. At least one reader and four Sweethome editors have experienced this failure, and none of us had any luck with Pur’s suggested remedies. But after speaking at length with a Pur representative, we have some better news to report.
First, if you have experienced this problem, call Pur customer service at 800-787-5463, and the company “will make it right,” in the representative’s words. Second, the Maxion cartridge has been redesigned with ventilation slots that “greatly reduce issues with clogging over the life of the filter.” The new cartridges will, according to Pur, go on sale sometime between April and October 2017; we’ll update this guide when they become available. For now, because of its great performance when it isn’t clogged, we’re sticking with the Pur Classic as our top pick.
A slightly less effective filter
Our runner-up, the Mavea Elemaris XL, is not as effective as the Pur on overall filtration, but in other areas it actually tops the Pur. With a pour-through lid (meaning you don’t have to lift a lid-flap to let water in), it is even easier to fill than the Pur. It also has the most comfortable handle we tested and four rubber feet that add just the right amount of friction for a solid feel on the fridge shelf, while still being easy for you to slide. Multiple color options set it apart from all the other pitchers we tested, which are largely limited to white. And Mavea’s recycling program—you drop used filters in local collection boxes or ship them back using free-shipping labels—is a nice, unique touch.
Like the Pur, the Mavea gives a good pour (with a removable flap over the spout) and got excellent subjective taste ratings. The filter is a simple friction fit and is easy to install and remove. Filling the top tank, however, only nets you three-fifths of a pitcher of filtered water—on the low end for our test models. Compared to the Pur and others, you’ll have to refill this at the faucet more often if you want an ample supply of filtered water in the reservoir.
Where the Mavea falters is on NSF certifications for filtration and on cost of ownership. These are not huge flaws but they were significant enough for us to conclude that the Pur is the clear first choice. Against the Pur’s 10 certifications for contaminant removal, the Mavea has seven (cadmium, copper, mercury, atrazine, benzene, simazine, tetrachloroethylene) plus the usual filtration for chlorine, which helps with taste and odor. Unlike the Pur, it is not NSF certified for cysts (cryptosporidium or giardia bacteria), carbon tetrachloride, or 2,4-D. And in our independent test, the Mavea removed 73 percent of the lead in our heavily concentrated sample—not a bad performance in itself, but not nearly as impressive as the Pur’s 97 percent. Finally, its filters are on average about 20 percent more expensive than the Pur’s.
How we tested
We evaluated each pitcher on two subjective measures—taste and ease of use—and several objective ones, including speed of filtration, filter capacity, and, of course, the quality of filtration itself. Because all our test pitchers had NSF 42 certification and most had NSF 53 certification, we didn’t retest every single thing they can filter out. Instead, we limited our testing to a few factors we felt would matter most to readers. We focused on removal of chlorine, which has a big impact on water’s taste and smell, and we looked at the ability to remove “total dissolved solids”—basically, mineral salts and organic matter. For our top two picks, we added an independent test for lead removal.
These pitchers typically use an activated-carbon filter and some also use an ion-exchange filter. Briefly, an activated-carbon filter works by trapping pollutants in its high surface area via a chemical process called adsorption. Activated carbon is effective at adsorbing organic compounds, including taste compounds. Ion-exchange filters contain high-surface-area polymer beads that remove inorganic contaminants and heavy metal ions such as lead, cadmium, and mercury, and release small amounts of harmless sodium and potassium ions. You may remember sodium and potassium from biology class: the Na-K pump (Na = sodium, K = potassium) across nerve-cell walls creates the electrical nerve signal, so you need these ions to survive.
We used three water sources for our tests: tap water from the kitchen faucet in our 1960s San Diego ranch house as a positive control (unfiltered water with the most contaminants), water from our fridge dispenser (in-line filter), and lab-grade reverse-osmosis-purified water as a negative control (super-clean water).
Prior to testing I washed the pitchers by hand with dish soap, rinsed them, and dried them. While the pitchers were drying, I soaked the filters in cool tap water for 15 minutes, then flushed them under cool tap water for 10 seconds. Next, I installed the filters according to the manufacturer’s directions and filled the pitchers with water and discarded the water three times to remove any loose carbon dust. I then used water collected from the fourth fill for the following tests.
For the chlorine test, we tested water samples for temperature with a digital thermometer (roughly 20 degrees Celsius/68 degrees Fahrenheit), then measured chlorine levels by inserting a test strip from Industrial Test Systems and color-matching the results according to the manufacturer’s directions. We also measured the samples’ pH using indicator strips and found it to be neutral in all cases. We used an HM Digital TDS-EZ meter to measure total dissolved solids at the parts-per-million level (ppm).
Taste and ease of use are subjective measures, of course. My wife and I tasted filtered samples from each pitcher two times and ranked them for overall good taste and lack of chlorine odor. We also ranked the pitchers’ usability on factors such as ease of filling and pouring, ease of replacing the filters and lids, and ergonomics.
|Model||TDS||Total Chlorine (ppm)||Chlorine Reduction (%)||Time to Filter 1 Liter (min:sec)||Subjective Taste Rank Order (1 = best)||Usability (1 = best)||Overall Rank|
|Lab Reverse-Osmosis (RO) Water||31||0.0||100%||n/a||1||n/a||Excellent|
Summary of objective testing
For total dissolved solids, our tap-water control measured 406 ppm. One way to understand this measurement is with the analogy that one ppm is equal to one minute in two years. Most of the filtered water samples were close to this—at most 25 percent lower. The exceptions were the reverse-osmosis control and ZeroWater samples, which were near zero (30 ppm) and actually zero, respectively. However, ZeroWater specifically targets TDS and the others do not. Moreover, dissolved solids are objectively not a bad thing and possibly an objectively good one—see the last paragraph of Contaminants that could be in your water below.
Total chlorine was high in the tap-water control (0.65 ppm; the EPA limit is 4.0 ppm). Soma (0.35 ppm), Clear2O gravity (0.3 ppm), my fridge (0.2 ppm), Clear2O faucet (0.175 ppm), and the Brita pitcher (0.1 ppm) left significant amounts of chlorine in the water after filtration. Our pick and runner-up reduced chlorine to zero or near zero (less than 0.03 ppm).
Comparing the taste rankings to the amount of time to filter reveals a pattern: Longer filtration times are associated with better taste and shorter filtration times with worse taste. Mavea, Pur, and ZeroWater all took more than five minutes to complete one filtration cycle—and they all tied for second in terms of lack of chlorine taste, bested only by the lab-pure reverse-osmosis water. Soma, Clear2O gravity, and Brita, by contrast, filtered in the one-to-two-minute range—and ranked a distant fifth through seventh place for taste. This makes sense: Longer filtration times mean more time for contaminants to be adsorbed and absorbed by the filters. It’s interesting to see that principle so plainly illustrated in reality.
Longer filtration times are associated with better taste, and shorter filtration times with worse taste.
Lastly, but not shown in the table, is a useful ratio that we calculated for each pitcher: the volume of the top “fill tank” relative to the volume of the bottom “filtered tank.” That ratio varied widely, from a worst of 0.46 for the ZeroWater to a best of 0.73 for the Pur. In plain terms: You don’t even get half a pitcher of filtered water each time you fill the ZeroWater’s top tank, but you get almost three-quarters of a pitcher of filtered water every time you fill the Pur.
Independent lead test
Based on our tests and NSF certifications, we decided to conduct independent lead testing on our top two filters: the Pur Classic and the Mavea Elemaris XL, which both scored at or near the top on taste and ease of use and in our own tests of filtration performance.
The EPA’s actionable limit for lead in drinking water is 15 parts per billion, or 0.015 mg/L. Continuing the time analogy above, one ppb is equivalent to three seconds in 100 years. If it is above that level in more than 10 percent of tests, the public is notified and the water-treatment-system operators must take a number of steps to improve the water’s quality. When the NSF tests filters for lead removal, it begins with a lead level ten times higher than that (0.15 mg/L) and requires that the filter reduce it to below the EPA limit to 0.010 mg/L.
Moreover, the NSF requires filters to maintain that performance for either 120 percent or 200 percent of their listed gallon capacity, depending on how the filter measures how much water has passed through it. For the Pur and Mavea, both rated at 40 gallons, that means they meet NSF Standard 53 after filtering 80 gallons—twice their rated capacity. (For more on how filters measure the amount of water that has passed through them, see When to change your filter below.)
However (and happily), the municipal water in San Diego has undetectable levels of lead, so in order to test the filters’ effectiveness, we had to artificially raise our water’s lead levels. Because we were testing only a single pass rather than a full life cycle, we also decided to start with a super-concentrated lead solution. I dissolved 10 mg of lead shavings (from a fishing sinker) with a 50-50 mix of white vinegar and hydrogen peroxide to form 40 milliliters of water-soluble lead acetate. I then mixed the lead acetate solution with tap water to make a one-gallon stock solution with target concentration more than 10 times above the NSF’s 0.15 mg/L test solution.
EnviroMatrix, a local certified testing lab accredited by the California Department of Health Services’ Environmental Laboratory Accreditation Program (ELAP #1931), performed the tests for lead reduction using an inductively coupled plasma mass spectrometer (ICP-MS). We tested by filtering 0.75 liters of the lead-rich water through each pitcher, disposing of the contents into an aqueous-waste container, then filtering a second 0.75 liters and using it for testing.
The results indicated that the control solution—our lead-doped tap water—had a lead concentration of 2.39 mg/L, or 2,390 ppb. In other words, we began our lead testing with a lead concentration 160 times higher than what the EPA considers unsafe and 16 times higher than the NSF test concentration. For comparison, 90 percent of homes in Flint, Michigan, had lead levels in their water of 27 ppb or less, though a team of researchers from Virginia Tech measured the highest level of lead in one home at 13,000 ppb.
We began our lead testing with a lead concentration 160 times higher than what the EPA considers unsafe.
Despite this heavy concentration, the Pur was able to reduce the lead levels by 97 percent to 0.073 mg/L. That is still seven times higher than the NSF Standard 53 requirement of 0.010 mg/L, but it’s way down from the highly elevated starting point. The Mavea substantially reduced the lead concentration as well—by 73 percent, down to 0.635 mg/L (60 times higher than NSF certification levels).
Again, the NSF Standard 53 test requires a 93.3-percent reduction of a 0.15 mg/L solution in order to pass—and the Pur achieved a significantly better percentage reduction than that on a water sample with 16 times more lead in it. However, given that the Pur is not officially certified by NSF to remove lead and our test was at a single point (versus an ongoing test over the life of the filter), we cannot formally recommend it if you have a serious lead-contamination issue.
Here’s a PDF of the test results from EnviroMatrix.
Brita is so synonymous with filter pitchers that the name itself has practically become generic English, like Kleenex and Band-Aid. But based on our tests and NSF certifications, you can do a lot better than the category leader. We tested the flagship Brita Everyday Water Filter Pitcher in the 10-cup size and found it to be inferior to the competition on filtration performance. In our test, it left behind a significant amount of chlorine (see Table 1), which manifested in its low score on water taste. And it is only NSF 53 certified for three contaminants (mercury, copper, and cadmium)—our pick is certified to remove 10. Compared to our pick and runner-up, we also found the Brita lacking in the usability department, with an uncomfortable, awkward handle shape and hard-to-separate components that make the unit relatively difficult to clean. Using a Brita you’ll spend more time at the faucet than you will with our pick: When you completely fill the upper tank on the Brita, not as much water drips down into the reservoir compared to the Pur, regardless of whether you look at it as a total amount of water or as a percentage of the reservoir’s capacity. The Pur does everything better than the Brita, at a nearly identical price. The Mavea does everything better for just a bit more.
The Pur does everything better than the Brita, at a nearly identical price.
Clear2O made a name for itself with its CWS100AW, a highly regarded filter pitcher (Consumer Reports rates it near the top of its list). It’s unique to this test in that it uses pressurized water from the faucet, rather than gravity, to force water through the filter. As a result, Clear2O uses a compressed block of activated charcoal rather than loose granules and that results in truly spectacular NSF 53 certifications: 38 of them, including lead, mercury, cadmium, and a host of organic compounds (biocides and petrochemicals for the most part). It also filters a liter of water in just 17 seconds, far and away the fastest in our test. So why don’t we recommend it? Because its faucet system is fussy—it was my least favorite to use—and involves permanently installing a special nozzle on your faucet and attaching it via a collar coupling to a hose on the pitcher every time you want fresh water. What’s more, the nozzle doesn’t fit on every faucet and we couldn’t confirm that it fits on any pull-down faucet. Lastly, the company is shifting its focus to a new line of gravity-fed filters, and though they promise to always keep the CWS100AW (or something similar) on the roster, that’s a bit unnerving.
We also tested the new Clear2O gravity-fed pitcher, the GRP200. It is NSF 42 certified for removal of chlorine taste and odor but not yet NSF 53 certified for any contaminant. It’s generally easy to use, but not spectacular or terrible in any aspect. Until NSF 53 results are available, we’ll leave it at that.
The Soma pitcher is a stylish member of a usually soulless category. However, it’s lacking in substance. Although the Water Quality Association certified it to meet NSF 42 standards for chlorine removal and taste, it is not NSF 53 certified, which all the other filters we tested are. (Update: As of October 2016, the Soma filter is WQA-certified to NSF 53 standards for copper and mercury.) In use we found it tricky to pull apart for cleaning, and the wide spout made for problems when doing pouring that required precision (such as filling a drinking bottle). And despite meeting NSF 42 standards, the one-stage charcoal filter did the worst job of removing chlorine of any filter we tested—even the one in my fridge. Unless style is your chief concern, take a pass.
Cleaning 40 gallons of water with a ZeroWater costs about $45 while the Pur and Mavea do it for about $5 and $7.
The ZeroWater ZP-010 10-cup pitcher is the only gravity-fed model we tested that is NSF 53 certified to remove lead. However, it has a number of flaws, so we only recommend it if you really need that feature. We found it extremely difficult to use because the lid has a tight fit and no lip to push on, making the lid hard to remove for filling. Instead, you must squeeze the tip of the lid tightly and rely on a friction grip to get it open. (This is, amazingly, by design: The lid is supposed to be watertight so that you can pour filtered water while the top tank is still partially full. It’s a poor trade-off.) Moreover, when trying to pour out the last cupful of water we repeatedly had problems with the filter and fill housing falling out and onto our hands, glass, or the counter. This hurts since the filter is very heavy, and it’s also incredibly annoying. And despite its beefiness the filter is NSF 53 certified for only three substances (lead, of course, and chromium and mercury), versus the Pur’s 10 and the Mavea’s seven. It’s also rated for a mere 15 gallons, versus 40 or more gallons for all the other filters in our test. And that fact only looks worse when you consider the cost of a ZeroWater filter: about $15. In other words, cleaning 40 gallons of water with a ZeroWater pitcher costs about $45 while the Pur and Mavea pitchers do it for about $5 and $7, respectively. Lastly, there are enough customer complaints about the ZeroWater producing a “fishy smell” that the company addresses the matter on its FAQ page.
How to find out if your water is safe to drink
US tap water is highly regulated by the Environmental Protection Agency and is generally of extremely high quality. Our public water supplies are a critical resource and are carefully monitored, with thousands of tests performed each year for up to 40 or more compounds. Once a year, customers are required to be notified of the testing results via a Customer Confidence Report. Copies of these can often be found online via this tool. See this example CCR for my local municipal water supply in San Diego. The CCR details where your water comes from, how it is treated, and its test results. In 2014, for example, San Diego’s water supply was tested 6,779 times throughout the distribution system for total coliform and E. coli, with an average of 0.1 percent of samples testing positive (the range was 0.0 percent to 0.3 percent). And please note that “testing positive” and “being dangerous” are not the same thing.
But even careful EPA testing is not the end of the story, as the Flint water crisis makes plain. Water leaves municipal treatment plants in beautiful condition—but that doesn’t mean it arrives at your faucets that way. Lead pipes, leaded pipe solder, leaking water mains—these factors and more can introduce contaminants as water makes its way to and through your home. Quite literally, water quality can change from door to door, sometimes dramatically. So even though part of the CCR protocol involves testing the most at-risk end-user locations, it can’t necessarily tell you the quality of your water.
But even careful EPA testing is not the end of the story, as the Flint water crisis makes plain.
Bottom line: If you are concerned about the safety of your drinking water, whether due to lead contamination or other issues, it is important to have it tested. You could start with a simple test kit for less than $20 or collect samples and have them fully characterized by an EPA-certified laboratory for $200 to $300. If you own a well, the state of California put together a great guide that tells how and when to test your water and what to test it for.
Contaminants that could be in your water
Lead is on everyone’s mind after Flint, and it is common in older plumbing—but older is younger than you might think. Only in June 1986 did the Safe Drinking Water Act declare that plumbing must be “lead free,” defined as solder and flux no greater than 0.2 percent lead and pipes and fittings no greater than 8 percent lead. (The 2011 Reduction of Lead in Drinking Water Act reduced this “wetted lead” from 8 percent to less than 0.25 percent.) But lead in plumbing does not equate to high levels of lead in the water—that’s a matter of various contributing factors like pH—and municipal water supplies are often doped with harmless chemicals that help “lock” the lead in the pipes and solder. (The issue in Flint is that these chemicals were removed, releasing the lead.)
The list of other potential contaminants is long. Some of the more common or familiar ones are mercury, cadmium, benzene, nitrates from fertilizers, and the generic herbicide 2,4-D (now in use for more than 70 years). At our request, Rick Andrew, NSF International’s director of global business development for water systems, prepared a very useful document listing the chemicals it typically tests for when conducting Standard 42 and 53 certifications. This previously unavailable document details for each chemical the starting concentration and required ending concentration to pass the test. The required reduction can vary dramatically chemical by chemical—testing requires a 93.3-percent reduction for lead but only a 50-percent reduction in chlorine, for example.
In recent years the NSF has identified some pharmaceuticals and other common compounds (BPA and DEET, for example) as “emerging contaminants” and has created a new test for them (Standard 401). The test is not common in water-filter testing yet, but may become so.
One last thing that is certainly in your water, but certainly not a problem, are the generic total dissolved solids. Again, these are dissolved minerals and organic matter. According to the World Health Organization, “The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogen carbonate, chloride, sulfate, and nitrate anions.” If many of these elements sound familiar, it’s because you can find a lot of them in a bottle of vitamins. The WHO further notes that studies indicate that higher TDS in drinking water is associated with lower incidence of cancer and heart disease. Besides, as the WHO says, “Water with extremely low concentrations of TDS may also be unacceptable because of its flat, insipid taste.” In short: At the levels typically found in drinking water, total dissolved solids are healthy and make the water taste good. ZeroWater, one of the pitchers in our test, makes a big point of reducing TDS to zero. That’s not self-evidently a good thing.
When to change your filter
Many filter pitchers, including our pick and runner-up, feature an indicator (usually a little LED or LCD display) that tells you when the filter needs to be changed. But while filters are rated by the volume of water they can clean, the indicators are almost always simple clocks—they measure the amount of time that a filter has been in use and use that as a proxy for volume. That’s the case for our pick and runner-up, the Pur and the Mavea, respectively. (The Clear2O pitchers are a rare exception: They actually measure volume.)
Typically, two months of use is assumed to equate to 40 gallons of water filtered, the most common rating capacity. But, of course, that’s just an estimate or average. Your usage may vary by a lot, depending on how many people use the pitcher, how much of a hydrator you are, and so on. If you really want to be sure, the only way is to measure your actual water usage. Try keeping track for a week and divide the rated capacity (40 gallons for the Pur and the Mavea) by the gallons of water you actually used. That’ll tell you how many weeks you should use each filter before replacing it.
But also remember, as noted above, that the NSF forces filters that use a clock-based change-filter indicator, like the Pur and the Mavea do, to perform to Standards 42 and 53 for twice their actual gallon rating. And volume-measuring filters like the Clear2O have to perform for 20 percent more than their rated capacity.
The upshot? You can be pretty darn forgetful or lazy about replacing your filters—and really, who of us isn’t?—and still be confident that you’re drinking clean water.
1. “NSF Certified” means a filter has passed NSF tests. Filter makers who failed the tests often use the misleading phrase “tested to NSF standards.” Using the phrase is such a widespread practice that the NSF’s website has a page devoted to it. Jump back.