After 30 hours of reporting and research, we believe the Filtrete Maximum Under Sink Water Filtration System With Dedicated Faucet is the best under-sink water filter for most people. Of the hundreds of filters we compared, few can remove as many contaminants, and the Filtrete is easily the most affordable of its kind.
*At the time of publishing, the price was $44
For this guide, which didn’t involve testing, we looked at the most common type of under-sink filter: the kind that uses activated charcoal as the main decontaminant. Hundreds are available, but our pick, the Filtrete Maximum Under Sink Water Filtration System With Dedicated Faucet, is one of the few that meets three strict NSF standards for a wide range of pollutants, including lead and some pharmaceuticals. Most filters that meet these qualifications cost hundreds or even thousands of dollars, but the complete Filtrete system, including a faucet, currently costs about $50. It’s also easy to install and affordable to maintain, with replacement filters that currently cost about $20 apiece, last six months, and can handle 750 gallons—easily enough to satisfy a thirsty family of four for half the year.
I co-authored our guide to pitcher-style water filters, and it turned out much of the research and reporting I did there applies to the under-sink filters I looked at for this guide, too. The basic technology is the same, and so are the NSF standards and tests they’re held to. This said, I had to do a complete crash course on the under-sink category: Unlike the quite limited number of pitcher filters, there are hundreds if not thousands of under-sink filters, each with strengths and weaknesses. In the end, separating the mediocre from the great required a multipronged approach: First, I used NSF’s handy search engine to find a group of candidates that met our criteria for pollution removal; then I searched user and expert reviews to find the ones with the best reputations for functionality and durability; and finally, I reviewed my research at length with a water-quality expert, Steve Richards of Aqua Source Group, who helped me confirm my picks (and steered me clear of a few mistaken assumptions I’d made).
As laid out in detail in our guide to pitcher-style water filters, most Americans’ tap water is perfectly healthy, so in terms of absolute need, the answer is “probably not.”
All US municipal tap water leaves the local water-treatment plant having been tested to stringent federal standards for dozens of potential pollutants and pathogens, from lead and E. coli to a gallery of pesticides. As it flows toward homes and businesses, the water in the mains is also routinely monitored. (New York City conducts almost 1,000 such tests every day—in 2015, no violation of federal standards occurred.)
Simply put, when US tap water goes bad, it’s most often the result of nasty stuff getting into it within the home. Older homes are more vulnerable to problems than new homes, largely due to the use of lead-rich solder (outlawed in 1986) and, in buildings more than a century old, even solid-lead pipes. Utilities take—or should take—steps to lower the probability of lead leaching out of these sources. But they sometimes fail to. That’s what happened in Flint, Michigan: After switching from Detroit’s municipal supply to water from the more-acidic Flint River, the Flint utility failed to add a crucial chemical treatment, orthophosphate, to the water it delivered to customers. Orthophosphate helps “lock in place” the lead present in the pipes of older cities and homes. Without it, the Flint River water began leaching that lead out, resulting in the lead-poisoning crisis. (Chemical & Engineering News has an excellent in-depth article on these events.)
To get a better idea of what, if anything, is in your water, you can request a free “consumer confidence report” from your local utility; it will tell you the exact composition of the water that leaves the treatment plant that serves your address. For ultimate peace of mind, you can also have a local lab test the water that flows from your taps (expect to pay several hundred dollars for the service).
If you’ve decided you want certifiably “pure” water, you have multiple options. You can get a water service, delivering filtered water in bottles to your fridge or in 5-gallon carboys to a dispenser. You can get a whole-house or—in industry terms—point-of-entry filtration system, but these are mostly aimed at people with exceptionally hard (aka, mineral-rich) water. You can get a pitcher filter (we have tested them and have recommendations), or a countertop unit. You may also be able to install a filter in your fridge’s dispenser. Or you can get an under-sink (“point-of-use”) system.
Pitchers and under-sink filters both work the same way: Water flows through a canister containing activated charcoal and, often, an ion-exchange mechanism made of a specialized resin. The charcoal removes organic compounds, like pesticides, and particulate matter; the ion-exchange resin removes dissolved metals,1 with lead being the one most people are concerned about. (For details on how they work, see our filter-pitcher guide.) The other main class of under-sink filters, reverse osmosis, is not this guide’s focus—here’s why.
Both types are highly effective, but an under-sink system has a few advantages:
Convenience: You can get filtered water instantly just by turning on a faucet, versus having to wait for a pitcher to do its work. That includes saving the time it takes to to open the fridge, fill the pitcher, heave it out of the sink, and put it back in.
Capacity and speed: The highest-capacity under-sink filters can clean 1,000 gallons of water or more; most pitcher filters are rated to just 40 gallons. That means some under-sink filters can go for a year between replacement, whereas a thirsty family of four might need to replace a pitcher filter once a month. (The difference comes down to water pressure. A pitcher filter relies on gravity to draw water through the filter, and that means the charcoal filter has to be composed of loose beads or pellets—otherwise you’d wait all day for a drink. Under-sink filters, by contrast, push relatively high water pressure through a solid block of charcoal, which uses increased surface area and finer perforations to greatly boost the filtration capacity.)
Functionality: Almost anyone can operate a faucet; pitchers can be too heavy and unwieldy for kids and people with arthritis or difficulty with lifting.
Under-sink filters also have some disadvantages:
Size: Under-sink filters take up valuable storage space under the sink. It may not be much—our pick is about the size of a wine bottle, and it’s suspended under the sink, off the cabinet bottom—but it’s a consideration.
Installation: If you’re reasonably handy and have a sink that’s ready to accept an additional faucet—it’ll have an extra hole besides the main faucet, where a soap dispenser (for example) can be put in—you should be able to install an under-sink filter yourself. If not, you’ll probably need to hire a plumber. (Once the filter is plumbed in, you’ll be able to replace filters yourself—most, including our pick, have a simple twist-on-twist-off design.)
Temperature: Water from an under-sink filter is not as cold as water poured from a refrigerated pitcher, or filtered water from a refrigerator’s dispenser. (You’ve got filtered ice, right?)
If, having weighed these factors, you’re still interested in an under-sink filter … read on.
By far the most important quality of a water filter is its certified ability to remove unwanted chemicals and pathogens. That word “certified” may seem self-evident, but makers of noncertified filters use convincing language to disguise the fact that their products don’t really do much. So we went right to the industry-standard, independent certifier: NSF International. (You’ve probably seen its logo on some of your cookware—among many other things, NSF certifies kitchen equipment for safety and sanitation.) Manufacturers pay to have NSF test their products, and not every water-filter maker ponies up; when one does, it’s a sign that the manufacturer stands by its product.
Using NSF’s handy, er, filter tool, we pulled up all the under-sink filters that have achieved NSF Standard 53 certification,2 which indicates a filter passed rigorous tests and is known to reduce the levels of a given metallic or organic pollutant to below federally mandated levels.
We also looked at a new NSF category, 401, for “emerging contaminants”—which include pharmaceuticals and estrogen-mimicking compounds. The EPA and others are concerned about the penetration of drugs and estrogen mimics into the water supply, and NSF created Standard 401 in response. Not many carbon-block filters are certified for Standard 401 yet—fewer than 40 at the time of writing—but our pick is one of them.
All the filters we considered are also NSF 42 certified, which means they reduce chlorine and thus improve taste and odor, a simple process and one that NSF classifies as “aesthetic.” (Most water utilities use chlorine to kill germs in the supply.)
Within each standard, filters are certified for specific contaminants. One filter might be certified under NSF 53 to treat only mercury, for example. Another might be certified for several pesticides under NSF 53, but not be certified for mercury. We insisted only on lead and cyst (bacteria) certification, but we favored filters that reduced a wider range of contaminants, including pesticides, industrial chemicals, and drugs.
Filter capacity also narrowed our choices. Most under-sink filters are rated at 100 or 300 gallons, but a few go as high as 1,000 gallons or a bit more. High capacity means fewer filter changes (and less worry about whether it’s time to change the filter—just set an annual or semiannual calendar reminder). So we focused on 500-plus-gallon models, which should meet a family of four’s needs for at least six months. (Note, however, that even if you haven’t gone through a filter’s rated capacity, you should still replace it according to the manufacturer’s recommended timeline. Bacteria can multiply inside filters, if given enough time; replacing the filters on schedule virtually eliminates that possibility.)
We also limited our search to filters that are attached to a separate faucet. Under-sink filters are either mounted “in-line,” meaning the filtered water comes out of the main (existing) tap, or are given their own dedicated tap. We strongly believe the dedicated faucet is a better option than an in-line filter: With a dedicated faucet, you can use filtered water for all your drinking and cooking needs, but you won’t waste the filter’s capacity on jobs that don’t need filtered water, like washing the dishes.3
Flow-rate was another factor. Under-sink filters tend to hover in the 0.5 to 0.75 gallons-per-minute range. That may not seem like much of a difference, but for comparison, the standard faucet in many sinks delivers 2.2 gpm. When filling a drinking glass or pot from the filtered faucet, a 50-percent-faster pour makes a big difference in how long you’re standing there waiting—so we favored 0.75 gpm models.
Upfront cost and the cost of replacement filters were also a concern, and under-sink filters range from less than $50 to nearly $2,000. So we aimed for the best overall value—but only after a filter met the criteria listed above.
Finally, because we wouldn’t be testing the candidate filters ourselves, we delved into user reviews and ratings, discarding any otherwise likely seeming models that got low ratings or frequent complaints about design flaws or difficult installation and maintenance. As always, we turned to reliable reported sources, including Consumer Reports, for further insights. And we spoke at length with Steve Richards of the Aqua Source Group, a water-treatment firm that’s served the Rochester, New York, area for almost 30 years. Richards has achieved many of the highest certifications offered by the Water Quality Association—among others, he’s a Master Water Specialist—and he answered our (many) in-depth questions about NSF standards, the various types of filters available, and the filters we considered for this guide.
One last thing: We’re assuming that you’re connected to a municipal water supply, which—again—are highly regulated and pretreated for contaminants. But if you draw water from a private well or other nonmunicipal source and are concerned about contaminants, you must consult a local water-quality expert for advice.
The Filtrete Maximum Under Sink Water Filtration System With Dedicated Faucet is our top choice for under-sink filters because it has a combination of price and filtration performance that’s unlike any of its competitors’.
It removes contaminants in three of NSF’s strict testing categories, including those for lead and pesticides, and a new category for “emerging contaminants” such as pharmaceuticals. That’s a rare distinction in itself: Fewer than 40 filters (among hundreds) of its type have been certified for emerging contaminants at the time of writing. The Filtrete is also the most affordable option by far, at about $50 for the complete system, including a faucet, and $40 per year in replacement filters; though other under-sink filters cost hundreds to buy and maintain, this is more comparable to our pitcher-filter pick’s pricing. The faucet is easy to install as long as you have a separate hole on your sink already (like for a soap dispenser or sprayer). Given all that, it’s a clear choice if you use a lot of filtered water—having nearly unlimited quantities on hand is a real convenience.
Specifically, the Filtrete is NSF 53-certified for six contaminants (lead, cyst/bacteria, atrazine, benzene, P-dichlorobenzene, and toxaphene). In the new NSF 401 “emerging contaminant” category, it is certified for five: carbamazepine, linuron, estrone, bisphenol A (BPA), and nonylphenol. (We lay out the sources and potential health effects of all these in Contaminants explained, below. We further argue that concerns about BPA’s health effects are misguided and overblown.) The Filtrete is also NSF 42-certified for reduction of chlorine taste and odor. Some filters are certified for a wider array of contaminants (see two of them in If you know your water is compromised, below), but given their price—these others cost hundreds of dollars upfront and in annual maintenance—and the generally high quality of the US municipal water supply, we think the Filtrete is the best option for most people.
Moreover, because the chemical-removal process is the same for many substances NSF tests for, the Filtrete system likely significantly reduces other pollutants too, if not officially to the stringent NSF standards. The thing is, NSF tests filters that use activated charcoal against contaminant concentrations that far exceed anything typically present in municipal water—and then only after pushing the filters to twice their rated capacity. So under real-world conditions (a filter fresh out of the box, and a water supply that’s fairly clean to begin with), performance is likely better than officially stated. We found this to be true when we tested pitcher-style charcoal-based filters; for example, we filled our top picks with an extremely lead-rich solution—160 times more polluted than FDA limits, and 16 times more than NSF’s test solution. Even though neither was NSF-certified for lead, our winner nonetheless removed 97 percent of the lead, and our runner-up removed a respectable 73 percent.
At its current price of about $50, the Filtrete is easily the most affordable under-sink filter that met our criteria, and it comes with all the hardware to install it, including a faucet. (You can also opt to hook it to a different faucet to match your decor.) The replacement filter, the 4US-MAXL-F01, currently costs about $20. By the recommended six-month replacement schedule, that means $40 a year in maintenance costs. For comparison, most of the other similarly certified systems we looked at cost $250 or more, with replacement filters coming in at at least $70, and not all of them came with a faucet. And compared with our pitcher-filter pick, the Pur Classic, annual filter costs for the Filtrete are in the the same ballpark—about $28 for the Pur, versus $40.
With 750 gallons of lifetime filtering capacity and 0.75 gpm of filtered-water delivery, the Filtrete is at the high end of both measures. Add in its generous six-month replacement schedule and you have a great combination of utility and ease of maintenance.
Both the complete Filtrete Maximum Under Sink Water Filtration System With Dedicated Faucet system and replacement 4US-MAXL-F01 filters are widely available; in addition to Amazon, you can order or pick up one from Home Depot, Walmart, and Lowe’s.4 If buying at a store, you’ll see it prominently labeled on the box as the “Maximum” filter. (Note: Avoid the “Standard” model, number 3US-PF01, which will not fit on our pick’s hardware and is rated only for chlorine odor-and-taste reduction [NSF 42]).
Installing the Filtrete is straightforward as long as your sink has an existing hole for a second faucet or soap dispenser: Shut off the cold-water inlet valve under the sink (usually on the right), disconnect your existing faucet, connect the Filtrete using the included hardware, and reconnect the existing faucet. (Filtrete created a handy video of the process.) We’ll repeat for emphasis: You must hook the Filtrete (or any other under-sink filter) to the cold water line. Filters work in the roughly 40 to 100 degrees Fahrenheit range; hot water compromises or destroys them; our expert source Steve Richards has seen many filters ruined that way. If you can’t tell which line is which beneath the sink, before disconnecting, run the hot water in the faucet, check the two supply lines with your hand, and avoid the warm one.
Once you’ve installed the hardware, subsequent filter replacement is dead-simple: Simply twist off the old one by hand and twist on the new—no tools necessary. You don’t even have to shut off the cold-water supply—the mounting bracket contains an automatic lockout mechanism. (Still, best to put down a towel to catch any stray drips from the old filter and the faucet line.)
The Filtrete is a relatively compact system. It consists of a single, cylindrical filter unit about the size of a wine bottle, plus a small bracket and short lengths of tubing to connect the filter to the feed line and dedicated faucet. Some other comparably certified under-sink systems include multiple and/or larger filters that take up far more under-sink space.
It also is very well reviewed by its users: It has a four-star rating (out of five) across 70-plus reviews on Amazon, and similarly high ratings on other retail sites.
In short, based on its mix of performance (by far the most important criteria), price, availability, and ease of installation and maintenance, we believe the Filtrete fits our mission of recommending the best product for most people.
The Filtrete has a couple of flaws common to under-sink filters. First, it delivers a meager 0.75 gpm of filtered water. Though that’s on the high end of under-sink filters, it’s a lot lower and slower than your unfiltered, standard faucet, which likely delivers something on the order of 2 gpm. In short: Expect to spend more time at the tap when filling glasses or pots with filtered water.
Because under-sink filters are plumbed from the main cold-water supply, they deliver water at whatever temperature your utility provides. In most parts of the US, that means your filtered tap will deliver a tepid glassful; for a truly cold drink, you’ll need to add ice.
The Filtrete system certifiably removes six organic pollutants and metals (NSF 53) and five “emerging pollutants” (NSF 401), and as laid out above, we believe it significantly reduces more. However, filters certified by NSF for a considerably wider range of contaminants do exist. With the caveat that you need to consider them only if you know you have a problem with the contaminants they’re certified for, we suggest two other systems:
The 3M Aqua-Pure Under-Sink Water Filtration System (AP-DWS1000) is NSF 53-certified to remove—in addition to lead and cyst—MTBE (a gasoline additive) and volatile organic compounds (VOC), a broad-brush category encompassing more than 40 organic substances common in the industrial-chemical and biocide industries (including all those our pick is certified for). The complete system, with all hardware, including a faucet, costs about $280 and is rated to 625 gallons; a set of replacement filters costs about $100. At the manufacturer’s six-month replacement schedule, that amounts to about $200 per year. Because the system uses a pair of filters, it also takes up more room under the sink than our pick. Installation and replacement is straightforward, similar to the Filtrete’s.
The Body Glove BG-12000 Water Filtration System is certified to numerous NSF 53 (metals and organic compounds) and six NSF 401 (“emerging contaminants”/pharmaceuticals) standards. It’s made by 3M.5 It costs about $400 and has no replacement filter; rated to 1,000 gallons, the entire unit has to be replaced yearly, meaning $400 is the annual cost. It’s about the size of a two-liter bottle of soda, so it doesn’t take up an egregious amount of room, but it does not come with a faucet—you’ll have to provide your own. Otherwise, installation is straightforward. And to answer the question in the air: Yes, that’s the same Body Glove whose totally rad fluorescent shirts Sweethome readers and writers of a certain age lusted after as teens. Body Glove is made up of surfers, and the company has a decades-long record of supporting clean-water initiatives.
Reverse osmosis is a filtration method that involves forcing water through an extraordinarily fine filtering membrane. Water molecules can pass through, but most contaminants simply cannot. Done right, it is exceptionally effective: Reverse-osmosis filters can remove many metals, including lead and chromium, and many pesticides and herbicides. The technology has been around for decades in laboratories (which often need ultrapure water) and desalination facilities, but in recent years costs have dropped to the point that under-sink reverse-osmosis filters are now available to homeowners. According to Richards, reverse osmosis now rivals the popularity of charcoal-based filtration (the kind our Filtrete pick uses).
So why did we not name a reverse-osmosis pick for this guide? Several reasons. One, frankly, is that we have never tested the technology ourselves, and without at least some hands-on time, we’re reluctant to speak with authority about it. (We applied a lot of what we learned during our tests of pitcher filters to make our decisions here.) Another is cost: Most reverse-osmosis systems cost hundreds of dollars—Consumer Reports’s top picks cost $1,800, $675, and $1,000, for example. Maintenance costs are also high, because reverse-osmosis systems typically have a pair of carbon-block pre-filters that need changing every six months, plus a pair of membrane filters that need to be changed annually or biannually. This adds up to a system that costs you major money for filtration of chemicals that likely don’t exist in your water to begin with.
Reverse-osmosis systems are also bulky, because in addition to multiple filters they include a reservoir for filtered water, generally a plastic tank of several gallons’ capacity. All this has to fit under your sink, which can get tricky in compact kitchens, whereas our pick can easily fit most anywhere.
Finally, reverse-osmosis filters constantly must drain a stream of concentrated, contaminated water—what’s left behind the membrane after it’s done its work—and from your drains it eventually reenters the environment. Charcoal filters, like our picks, “lock” contaminants in the filter itself; when they’ve completed their life cycles the filters can be disposed of in a sealed landfill.
However, none of these drawbacks change the basic fact that reverse-osmosis systems can be very, very good—and are increasingly a first choice among homeowners. We’re not ready to name a pick in this category yet, but we’ll continue to research the best options and will likely be ready to offer a specific product recommendation in a future update to this guide.
NSF lists the contaminants that a given filter is certified for, but if you don’t already know what the contaminants are, the lists don’t tell you anything about their sources and potential health effects. Here’s a brief rundown of the contaminants our pick, the Filtrete Maximum Under Sink Water Filtration System With Dedicated Faucet, is certified for, where they come from, and what their known health effects are. Below that is a selection of compounds our other filter picks are certified for.
NSF 53 (lead and other metals, and many pesticides and petrochemicals): Lead has been used for millennia in water pipes and, in recent times, solder (its elemental symbol, Pb, comes from the Roman Latin plumbum, from which we get “plumbing”). It is a known brain and nervous-system disruptor and especially dangerous for children. “Cyst” as used by NSF refers to cellular/bacterial pathogens, including cryptosporidium and giardia, but excludes viruses, which are much smaller; municipal water is treated to reduce all pathogens to safe levels. Benzene is a common precursor, or building block, for other compounds created by the chemical industry, and a known carcinogen. Atrazine is a ubiquitous herbicide with disputed health impacts. P-dichlorobenzene is a common disinfectant, pesticide, and chemical-industry precursor, and a suspected carcinogen. Toxaphene is a now-banned insecticide used throughout the 20th century; it persists in the environment for years and is toxic at high levels.
NSF 401 (“emerging contaminants”): Carbamazepine is a common drug used to treat various neurological disorders. Linuron is a common herbicide used to control grasses and weeds. Estrone is a form of estrogen that’s released into the environment by certain steroidal drugs and has known adverse health effects; in women it is a known carcinogen. Bisphenol-A (BPA) is used in the manufacture of plastics and resins, including those that line cans of food; it is highly controversial but we (and many, many others) believe its risks are minimal. Nonylphenol is a class of chemicals present in (among other things) detergents; it’s a potential endocrine disruptor.
Among the contaminants our picks in our “If you know your water is compromised” section are certified for are trihalomethanes (TTHM), a broad class of related compounds that, in municipal water supplies, are most often the byproduct of chlorination (a standard treatment to kill pathogens). Their health effects vary; some, like chloroform—a common chemical precursor—are suspected carcinogens. MTBE is a gasoline additive that helps reduce engine knocking and increase fuel combustion; its health effects are debated but it is known to be widely present in groundwater. VOCs, as defined by NSF for Category 53, is a class of more than 40 organic substances that includes many biocides and industrial chemicals. An NSF 53 VOC certification means that a filter significantly reduces all of them.
Broadly speaking, this guide is the result of a process of elimination: We insisted on NSF 53 certification (for lead and other metals, cyst/bacteria, and many pesticides and petrochemicals), and favored NSF 401 certification (“emerging contaminants,” including drugs). We also insisted on NSF 42 certification for removal of chlorine taste and odor, though that’s not difficult to achieve (NSF considers 42 an “aesthetic” category). This eliminated hundreds, possibly thousands, of filters off the bat. (If you own a water filter already and want to see which contaminants it’s certified for, visit the NSF search page and enter your filter cartridge’s ID number or brand name.)
We were left with several hundred contenders, which we winnowed down to a handful based on the factors listed above in How we picked. Our list of finalists, it turned out, included two of Consumer Reports’s top recommendations. One was the 3M Aqua-Pure Under-Sink Water Filtration System (AP-DWS1000), described above.
The other is the Multipure Aquaversa (MP750SB) under-sink filter with faucet. It has a very strong list of NSF 53 and 401 certifications, and a high 750-gallon capacity and 0.75 gpm flow rate (both equal to our main pick). However, at about $430 for the system and $70 per replacement filter, versus our pick’s $50 and $20, its costs outweigh its performance for most people.
(Photos by Michael Hession.)
Originally published: October 10, 2016
We're gonna have to have a whistle-off!