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        Anyone who drinks more than a few gallons of drinking water per day will likely be most satisfied with an under-sink filtration system like the Aquasana AQ-5200. Unlike a jug, an under-sink filter provides a continuous supply of water on demand. We recommend the Aquasana AQ-5200 because its certifications are the best of any system we found; they include (like the rest of our solutions here) chlorine, lead, mercury, PFAS, a variety of pesticides, and microplastics.
        The Aquasana AQ-5200 is ANSI/NSF certified and can virtually eliminate a wide range of contaminants, including lead, mercury, pesticides, microplastics, pharmaceuticals and other materials that few competitors can capture. It is one of the few filters certified to contain PFOA and PFOS, two persistent chemicals of concern to the Environmental Protection Agency.
        The cost to replace a set of filters is about $60, or $120 per year, based on Aquasana’s recommended six-month replacement cycle. And the system is only slightly larger than a few cans of soda, so it doesn’t take up much valuable space under the sink. It features high quality metal fittings and the faucets are available in a variety of finishes.
        AO Smith AO-US-200 is identical to Aquasana AQ-5200 in all important respects. (That’s because AO Smith acquired Aquasana in 2016.) It has the same premium features, all-metal hardware, and compact form factor, but since it’s only sold at Lowe’s, it’s not as widely available and its faucets have only one finish. : brushed nickel. Filter replacement costs are similar: about $60 per set, or $120 per year on the six-month cycle recommended by A.O. Smith.
       Has the same excellent certifications as the AQ-5200, plus higher flow and filtration capabilities than the AQ-5200, plus a pre-filter to remove rust deposits.
        The Aquasana AQ-5300+ Max Flow has the same excellent certifications as our top pick, but it offers higher flow (0.72 gpm vs. 0.5 gpm) and filtration capacity (800 gpm vs. 500). g.p.m). This makes it a suitable option for households that need large quantities of filtered water and want it as quickly as possible. It also adds a sediment pre-filter that the AQ-5200 doesn’t have; this can expand the contaminant filter at higher flow rates in homes with sediment-rich water. However, the AQ-5300+ (with filters the size of a three-liter bottle) is much larger than the AQ-5200, and the initial and filter replacement costs are slightly higher (about $80 per set or $160 per year). .
       Installs without drilling and delivers up to 1.5 gallons per minute of filtered water through existing faucets.
        Aquasana’s Claryum Direct Connect connects directly to existing faucets, making it a particularly attractive option for renters (who may be restricted from moving) and those unable to install a separate filter faucet. It doesn’t even have to be mounted on the wall of the cabinet under the sink, it just stands on its side. It has the same ANSI/NSF certifications as other Aquasana and AO Smith models and can deliver up to 1.5 gallons of filtered water per minute. This filter has a rated capacity of 784 gallons and should last approximately six months. But it does not have a sediment pre-filter. Therefore, if you have problems with sediment, this is not the best option as it can easily clog. And it’s large—20.5 x 4.5 inches—so if your sink cabinet is small or overcrowded, it may not fit.
       Has the same excellent certifications as the AQ-5200, plus higher flow and filtration capabilities than the AQ-5200, plus a pre-filter to remove rust deposits.
       Installs without drilling and delivers up to 1.5 gallons per minute of filtered water through existing faucets.
        I’ve been testing Wirecutter water filters since 2016. In my report, I spoke in detail with filter certification organizations to understand how their testing is conducted, and delved into their public databases to ensure that manufacturers’ claims are backed up by: Certified testing. I also spoke with representatives of several water filter manufacturers, including Aquasana/AO Smith, Filtrete, Brita and Pur, to dispute their claims. I’ve personally tried all of our options because overall reliability, durability, and usability are very important for a device that is used several times a day.
        Former NOAA scientist John Holecek researched and wrote the first Wirecutter water filter manual, conducted his own testing, commissioned further independent testing, and taught me much of what I know. My work is based on his work.
        Unfortunately, there is no universal answer to the question of whether you need a water filter or not. In the United States, public water supplies are regulated by the U.S. Environmental Protection Agency under the Clean Water Act, and water leaving public water treatment plants must meet strict quality standards. But not all potential pollutants are regulated. Additionally, contaminants can enter the water after it leaves the treatment plant, either through leaking pipes (PDF) or by leaching from the pipes themselves. Water treatment performed (or neglected) at the plant can exacerbate leaching in downstream pipelines, as happened in Flint, Michigan.
        To find out exactly what’s in your supplier’s water, you can usually search online for your local supplier’s EPA-approved consumer confidence report; otherwise, all public water suppliers are required to provide you with their CCRs upon request. But because of potential contamination downstream, the only way to determine what’s in your home’s water is to pay a local water quality lab to test it.
        As a general rule, the older your home or neighborhood, the greater the risk of downstream contamination. The Environmental Protection Agency reports that “homes built before 1986 are more likely to have lead pipes, fixtures and solder”—old, once-common materials that don’t meet current codes. Age also increases the likelihood of contamination of aging groundwater by previously regulated industries, which can pose a risk, especially when combined with age-related degradation of underground pipes.
        If your family uses more than two to three gallons of drinking water per day, an under-sink water filter may be a better choice than a pitcher filter. Under-sink systems deliver filtered drinking water on demand, eliminating the need to wait for the filtration process to complete as with a pitcher. On-demand filtration also means that an under-sink system can provide enough water for cooking—for example, you can fill a pot with filtered water to cook pasta, but you’ll never have to refill the pitcher for that purpose. .
        Compared to pitcher filters, under-sink filters tend to have a larger capacity and longer life—typically several hundred gallons and six months or more compared to the 40-gallon size of most pitcher filters and two months. Because under-sink filters use water pressure rather than gravity to push water through the filter, their filters can be denser and therefore remove a wider range of potential contaminants.
        The downside is that they are more expensive up front than pitcher filters, and replacement filters are also more expensive in absolute terms and on average over time. The system also takes up cabinet space under the sink that could otherwise be used for storage.
        Installing an under-sink filter requires basic plumbing and hardware installation, but the job is only easy if your sink already has an opening for a separate faucet. Otherwise, you will have to remove one of the built-in faucet locations (the raised disc on a steel sink or the marking on a synthetic stone sink). If you don’t have a knockout hole, you will have to drill a hole in the sink or in the countertop if your sink is undermounted. If you have a soap dispenser or hand sprayer on your sink, you can remove it and install a faucet. (Do not install the faucet where there is an air gap – this is to prevent dirty rinse water from entering the dishwasher.)
        Almost half of all tap water contains persistent chemicals. Here’s how to determine if you’re at risk and limit your exposure.
        This guide is about a specific type of under sink filter: those that use a cartridge filter. They take up very little space and are generally easy to install and maintain. They use adsorbent materials (usually activated carbon and ion exchange resins such as pitcher filters) to bind and neutralize contaminants. Most mount to a separate faucet (included), which means you’ll need a mounting hole in the countertop; The hole made for the spray hose will work, or you can drill a new hole. We’re not talking about faucet-mount filters, reverse osmosis systems, or other water pitchers or dispensers.
        To ensure we only recommend filters you can trust, we always insist that our selections are certified to the industry standard: ANSI/NSF. The American National Standards Institute and NSF International are private, nonprofit organizations that work with the Environmental Protection Agency, industry and other experts to develop rigorous quality standards and testing protocols for thousands of products, including water filters. The two main water filter certification laboratories are NSF International itself and the Water Quality Association (WQA). Both products are fully accredited by ANSI and the Canadian Standards Council in North America for ANSI/NSF certification testing, and both must adhere to the same standards and testing protocols. Only after using prepared “test” samples, which were much more contaminated than most tap water, did the filter last well beyond expected life and meet certification standards.
       In this guide, we’ll focus on filters that are certified for chlorine, lead, and volatile organic compounds (VOCs).
        Chlorine certification is important because chlorine is a common culprit in “bad odor” in tap water. But this is almost a blessing: almost all types of water filters are certified.
       Achieving lead certification is difficult because it means reducing lead-rich solutions by more than 99%.
        VOC certification is also challenging because it means the filter can actually remove more than 50 organic compounds, including many common biocides and industrial precursors. Not all under-sink filters have both certifications, so by focusing on filters with both certifications, we’ve identified filters that perform significantly better.
        We narrowed our search further and selected filters with additional certifications to the relatively new ANSI/NSF 401 standard, which covers emerging contaminants that are increasingly found in water in the United States, such as pharmaceuticals. Likewise, not all filters are 401 certified. Thus, those facilities that are 401 certified (as well as lead and VOC certified) are in a carefully selected group.
        Then, within this strict subset, we look for products with a minimum capacity of 500 gallons. This equates to approximately six months of filter life under heavy usage (2.75 gallons per day). This filtered water is sufficient for most households for daily drinking and cooking. (Manufacturers provide recommended filter replacement schedules, usually in months rather than gallons; we follow these recommendations in our estimates and cost calculations. We recommend always using original manufacturer replacement parts instead of third-party filters.)
        In the end, we weighed the initial cost of the entire system against the ongoing cost of replacing the filters. We have not set a price floor or ceiling, but our research has shown that while initial costs ranged from $100 to $1,250 and filter costs ranged from $60 to nearly $300, these differences did not translate into significantly superior performance. More expensive models. We’ve found several under-sink filters that cost less than $200 but still have excellent certifications and durability. These are the people who became our finalists. Among other things we are looking for:
        During our research, we occasionally received reports of catastrophic leaks from owners of under-sink water filters. Because the filter is connected to the cold water supply, if the connector or hose breaks, water may leak until the shut-off valve closes, so it could take hours or even days to discover the problem, resulting in serious consequences for you. Water damage. It’s not common, but when you’re considering purchasing an under-sink filter, you need to weigh the risks. If you purchased one, follow the installation instructions carefully, being careful not to twist the connectors incorrectly, and then slowly turn the water back on to check for leaks. For added peace of mind (solving all your plumbing problems, not just the under-sink filter), consider installing a smart leak detector.
        Reverse osmosis (R/O) filters initially have the same type of cartridge filter as the one we chose here, but add a secondary reverse osmosis filtration mechanism: a finely porous membrane that allows water to pass through but filters out dissolved minerals and other substances. substances.
        We may discuss R/O filters in more detail in a future tutorial. Here we categorically reject them. They have limited functional advantages over adsorption filters; they produce large volumes of wastewater (typically 4 gallons of waste “wash” water per gallon filtered), whereas adsorption filters produce no wastewater; They take up more space because, unlike adsorption filters, they use a 1 or 2 gallon tank to store filtered water; and they work much slower than under-sink adsorption filters.
        We have been laboratory testing water filters for the past several years, and the main takeaway from our testing is that ANSI/NSF certification is a reliable indicator of filter performance. This is not surprising given the extreme rigor of the certification tests. Since then, we have relied on ANSI/NSF certification to select competitors rather than our own limited testing.
        In 2018, we tested the popular Big Berkey water filtration system, which is not ANSI/NSF certified but claims to have been extensively tested to meet ANSI/NSF standards. This experience further strengthened our commitment to true ANSI/NSF certification and our distrust of “ANSI/NSF Verified” claims.
       Since then, including in 2019, our testing has focused on real-world usability and practical features and shortcomings that become apparent as you use the products.
        We chose Aquasana AQ-5200, also known as Aquasana Claryum Dual-Stage. By far its most important feature is that its filters have the best ANSI/NSF certifications among our competitors for chlorine, chloramines, lead, mercury, VOCs, numerous “emerging pollutants,” microplastics, and PFOA and PFOS. Additionally, the faucets and fixtures are made from durable metal, which is better than the plastic used by some other manufacturers. In addition, the system is extremely compact. Ultimately, the Aquasana AQ-5200 is one of the best options we’ve found for under-sink filters, with the entire system (filter, housing, faucet, and hardware) typically costing around $140 up front or a set of two. filter replacement for $60. This is less than many competitors with weaker certifications.
        ANSI/NSF Certification (PDF) for AQ-5200 Contains chlorine, which is used to kill pathogens in municipal water supplies and is the leading cause of “off-odor” in tap water; lead, which can leach from old pipes and pipe solder. ; mercury; Viable Cryptosporidium and Giardia, two potential pathogens; Chloramine is a persistent chlorine-ammonia disinfectant that is increasingly used in filtration plants in the southern United States. Pure chlorine decomposes quickly in warm water. AQ-5200 is also certified against 15 “emerging contaminants” that are increasingly appearing in water supplies, including BPA, ibuprofen and estrone (an estrogen used in birth control), microplastics, as well as PFOA and PFOS, industrial fluoride-based compounds. widely found in US tap water. It is also VOC certified. This means it can effectively remove over 50 different organic compounds, including many pesticides and industrial precursors.
        In addition to activated carbon and ion exchange resin (which are used in most, if not all, under-sink filters), Aquasana uses two additional filtration technologies to achieve certification. For chloramines, catalytic carbon is added, that is, activated carbon, which is porous and therefore more reactive, created by treating the carbon with a high-temperature gas. For cryptosporidium and giardia, Aquasana produces filters with pore sizes reduced to 0.5 microns, which is small enough to physically capture them.
        The certification of the Aquasana AQ-5200 filter was the main reason we chose it. But its design and materials also set it apart from others. The faucet is made of solid metal, as is the T-piece that connects the filter to the pipe. Some competitors use plastic for one or both of them, which reduces costs but increases the risk of button crossing and improper installation. The AQ-5200 uses compression fittings to create a tight, secure seal between the pipe and the plastic tube that carries water to the filter and faucet. Some competitors use simple fittings, which are less reliable. The AQ-5200 faucet is available in three finishes (brushed nickel, polished chrome and oil-brushed bronze), while some competitors leave you no choice.
        We also like the compact form factor of the AQ-5200 system. It uses a pair of filters, each slightly larger than a soda can; some other filters, including the Aquasana AQ-5300+ below, are designed for liter bottles. With the filter mounted on the mounting bracket, the AQ-5200 measures 9 inches high, 8 inches wide, and 4 inches deep; The Aquasana AQ-5300+ measures 13 x 12 x 4 inches. This means the AQ-5200 takes up significantly less under-sink cabinet space, allowing it to be installed in tight spaces where larger systems cannot be installed, leaving more under-sink storage space. You will need approximately 11 inches of vertical space (measured from the top of the cabinet down) to replace the filter and approximately 9 inches of free horizontal space along the cabinet walls to install the cabinet.
       The AQ-5200 has received excellent reviews as a water filter, earning 4.5 stars out of 5 out of over 800 reviews on the Aquasana website and 4.5 stars out of nearly 500 reviews at Home Depot.
        Finally, at a current price of around $140 for the entire system (usually priced around $100) and $60 for a set of replacement filters ($120 per year with a six-month replacement cycle), the Aquasana AQ-5200 is what we’re looking for need to. One of the best deals among the competition and hundreds of dollars cheaper than some models with less extensive certifications. The device has a timer that beeps when you need to change the filter, but we recommend that you also set regular calendar reminders on your phone. (You’re unlikely to miss this.)
        Compared to some competitors, the Aquasana AQ-5200 has a lower maximum flow rate (0.5 gpm vs. 0.72 or more) and a smaller capacity (500 gallons vs. 750 gallons or more). This is a direct result of the physically smaller filter size. Overall, we think these minor shortcomings are outweighed by its compact size. If you know you need higher flow and performance, the Aquasana AQ-5300+ is rated at 0.72 GPM and 800 gallons but has the same six-month filter replacement schedule, while the Aquasana Claryum Direct Connect has a flow rate of up to 1.5 gallons per minute. , the nominal flow rate is 1.5 gallons per minute. up to 784 gallons and six months.
        The operating instructions for the AQ-5200 system are a bit sketchy and some parts are not shown in the parts list or diagrams. This won’t bother most owners. Basically, all you have to do is connect a few pipes to the water supply and taps, and everything will more or less explain itself. (The exception is the stainless steel decorative washer, which is not listed; it is installed on the faucet first, followed by the thin rubber washer.) Honestly, from what we saw in our research. But we hope that the guidelines will be revised in the future. In the meantime, here is a video from Aquasana on how to install the AQ-5200.
        As mentioned above in the How We Chose section, under-sink water filters (including the AQ-5200) sometimes fail catastrophically, causing severe water damage if the problem is not detected and corrected quickly. Be especially careful when installing and not cross-connecting connectors and making sure hose connections are secure and then slowly turning the water back on so you can find and fix leaks before they turn into disasters. Smart leak detectors can detect catastrophic leaks, regardless of their cause, before they cause the worst damage.
        Like all of our models, the Aquasana AQ-5200 comes with its own stand-alone faucet, which may not suit your style. You can also install a separate faucet of your choice as long as the faucet connection size is ⅜ inch. But you need to compare its flow rate to the Aquasana’s 0.5 GPM because the filter’s certification is based on flow rate. Please note that technically, using your own faucet means your system is no longer ANSI/NSF certified.
        If you suspect your water contains sediment (an orange tint caused by rust is a clue; as well as past experience with any type of filter, including pitchers, that clog before their expected lifespan), you may want to check other similar filters. Aquasana AQ-5300 with an additional sediment pre-filter.
        Sold as a (prepare to be bitten) two-stage carbon block clean water filter for under-sink water filtration systems, the AO Smith AO-US-200 is functionally and physically identical to the top-of-the-line Aquasana AQ-5200 in all the important ways. It has the same ANS/NSF certifications (PDF), the same compact size, filtration technology, all-metal construction, compression fittings, 0.5 GPM flow rate, and 500 gallon capacity. It also usually comes with a set of replacement filters for about the same price. There’s nothing fishy about this: AO Smith acquired Aquasana in 2016 and, an AO Smith spokesperson told us, is “leveraging” Aquasana’s expertise and has no plans to phase out the Aquasana brand.