5 Best Under

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We carefully reviewed this guide in April 2023 to ensure all of our recommendations, tested and vetted by the Good Housekeeping Institute Home Improvement Lab, were available and correctly priced. We stand by our picks.

The experts at the Good Housekeeping Institute Home Improvement Lab regularly test all kinds of water filters, from water filter pitchers that live in your fridge to shower filters that attach directly to the showerhead. Those options have their benefits, but under-sink water filters are the type we recommend the most, since they offer the best combination of performance, value and ease-of-use.

As the name implies, under-sink water filters are installed in the cabinet under the kitchen sink, with the dispenser typically stationed next to your kitchen faucet. "The systems take up a bit of cabinet space, but they don't clutter the sink deck the way countertop filters do, and they’re not clunky like faucet-mounted filters," says Rachel Rothman, executive technical director at the Good Housekeeping Institute.

In addition to being streamlined and discreet, the under-sink water filters that make our list all do an excellent job of removing contaminants, without premature clogging.

Once you've perused our picks, read on for more advice from our experts, like what to know about the different filter types and how to determine the risk level of your home's drinking water. If you are looking for more updates to your kitchen space, check out our round-up of the best kitchen faucets.

Aquasana has staked its reputation as a leader in water filtration over the last quarter century — and the brand has routinely impressed our testers in the process. Its 3-stage under-sink filter earns top marks from our engineers thanks to its innovative multi-filtration technology, which is NSF-certified to capture 77 contaminants, including heavy metals, pesticides, pharmaceuticals and water treatment disinfectants. It's also one of the few filters out there certified to remove PFAS, which is a big reason why GH's Beauty, Health and Sustainability Lab Director, Birnur Aral, Ph.D., put this Aquasana in her own home. As she attests, the device does all that filtering without premature clogging or a drop in flow rate, even though she uses it for everything from cooking to filling the coffee machine each morning. We should note, however, the filter-replacement cost with this unit is more than most, so it's more expensive to operate throughout the year.

While we haven't tested this system, Culligan is a trusted name in water filtration with a well-established record from past Good Housekeeping reviews. Besides its low initial cost, replacement filters are relatively affordable. The system is certified to capture a wide range of contaminants, including lead, mercury and cysts, and it claims to reduce chlorine taste and odor. That said, its granular activated carbon filtration is not quite as robust as other top picks: For example, the filter is not certified to NSF standard 401, which covers pharmaceuticals, herbicides and pesticides. The EZ-Change can filter 500 gallons before needing a replacement. That's respectable for a bargain-priced filter, but less than the 700 to 800 gallons we see with other models, so the Culligan is better suited to smaller households.

Our engineers found that Waterdrop's tankless design saves space compared with traditional reverse osmosis (RO) systems and is more water efficient too. While we haven't run extensive home tests, past reports on RO technology support its efficacy at capturing contaminants. The Waterdrop is NSF 58 certified, one of the highest standards, so it can stand up to everything from heavy metals to pharmaceuticals to PFAS. Our pros like the device's intelligent design, including the filter light indicator on the faucet and the smart monitoring panel, which tells you the quantity of TDS, or total dissolved solids, being filtered out of your water. One caveat: Unlike other filters in this roundup, the Waterdrop is not intended for well water, since the presence of large particulates can cause clogging.

If cabinet storage space is at a premium in your kitchen, you’ll appreciate the compact design of MultiPure's under-sink water filter. In field tests, our experts noted that the 5.8" x 5.8" x 8.5" housing can be mounted to a cabinet wall, leaving plenty of room for other items under the sink. Initial installation was straightforward, and it's also easy to replace the filter. Certified to NSF standards 42, 53 and 401, the solid carbon block filter is excellent at capturing a wide range of contaminants. Our tester reported that, provided the filter is changed annually, flow rate remains strong and steady even during the summer months, when household water consumption peaks. However, the dispenser isn't quite as sturdy as those we've evaluated on other models.

The Brondell under-sink water filter costs less than many reverse osmosis (RO) systems. We're still completing our in-home evaluation, but initial assessments have been positive so far, especially the ease of setup and how simple it is to swap filters in and out. The Brondell, which is safe for well water, is also extremely compact for an RO system. As for expected performance, our engineers note that the system is certified under NSF/ANSI Standards 42, 53, 58 and 372. That means it will deliver crisp-tasing water, without any chlorine odors, while protecting against the vast majority of contaminants, including known concerns, like lead and pesticides, as well as emerging ones, like pharmaceuticals in the water supply. The certification also ensures the structural integrity of the system, so you won't have to worry about parts failing prematurely. Though the Brondell does waste some water in its filtering process, it is ten times more efficient than traditional RO systems, according to the brand. Our experts will verify that claim, and share any other relevant findings, as soon as testing is complete.

To narrow the list of contenders for this report, our experts considered only water filters certified by NSF International, the organization that develops public health standards and certification programs for the industry. Over the years, we have reviewed scores of data points, such as checking which NSF standard the filters are certified for (some standards cover only lead, like NSF 372, while others also include agricultural and industrial toxins, like NSF 401).

As part of our hands-on tests, our experts looked at such factors as flow rate and how easy it is to install and to replace the filter. We also took into consideration a brand's track record and reliability, drawing on decades of water filter testing in our homes and labs.

Under-sink water filters are also known as point-of-use filters, since they treat only water coming from a single source, typically the kitchen faucet. The basic mechanics are always the same, but there are a couple of variables to consider.

✔️ Filtration: The most common technology is activated carbon, in which a carbon-based filter acts like a magnet, absorbing contaminants from the water. Multi-stage filters might also include a pre-filter to remove larger sediment, as well as a second carbon filter to improve odor and taste. Reverse Osmosis (RO) is a newer type of filter that captures contaminants by pushing pressurized water through a semi-permeable membrane. The process is extremely effective, but it's more expensive and less efficient — and many systems require a tank that won't fit under your sink. Before you invest in an RO water filter, our experts recommend testing your water to determine whether a conventional filter will provide enough protection. You might also hear about ultrafiltration (UF), a technology that, like RO, forces water through semipermeable membranes. Because the pore size of the UF membranes is bigger, these systems don't capture all contaminants, including total dissolved solids (TDS) like chlorine and fluoride; we did not review any UF systems for this reason.

✔️ Installation: While every system is unique, most come with a filter housing that gets mounted to an inside wall of your sink cabinet. Always check the dimensions listed in our product reviews (or on the manufacturer's website) to ensure there's room in your cabinet. One end of the filter ties into your cold-water line via a flexible connection. A second connection goes from the other end of the filter to the dispenser, which sits on your sink deck. Installing the dispenser is often the trickiest part, since it involves drilling a hole in the countertop. Capable DIYers should be able to handle the project, but it might be worth calling in a plumber if you’re less experienced, especially if your water line needs to be modified.

✔️ Maintenance: The main consideration is filter replacement. Take note of the steps and costs that go into the process. Our pros look for models with long-lasting filters (400 gallons is good, 600-plus gallons even better), affordable replacement filters ($100 or less, per year) and simple "tool-free" swapping in and out of the filters.

Dan DiClerico has written about the residential water filter market for more than 20 years, reviewing dozens of models from every leading brand. He also keeps up with the latest innovations by attending trade shows and industry events, like CES and the Kitchen and Bath Industry Show. In his role as Director of Home Improvement & Outdoor at the Good Housekeeping Institute, Dan oversees water filter testing alongside our health and technical experts.

Rachel Rothman, Chief Technologist & Executive Technical Director at the Institute, added another 15 years of expertise to this project, leveraging her training in mechanical engineering and applied mathematics to understand the science of filtration. In recent years, she has also run home tests on half a dozen systems, providing real-world assessments around performance and usability over extended periods of time.

Having written thousands of product reviews and how-to articles on all aspects of home ownership, from routine maintenance to major renovations, Dan (he/him) brings more than 20 years of industry experience to his role as the director of the Home Improvement & Outdoor Lab at the Good Housekeeping Institute. A one-time roofer and a serial remodeler, Dan can often be found keeping house at his restored Brooklyn brownstone, where he lives with his wife and kids.

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