The Best Under-Sink Water Filter

If you consume more than a couple of gallons of water daily, an under-sink filtration system like the Aquasana AQ-5200 is ideal. It provides a continuous water supply and boasts top-notch certifications, filtering chlorine, lead, mercury, PFAS, pesticides, and microplastics.

Everything we recommend

The Aquasana AQ-5200 is ANSI/NSF-certified to remove a wide range of contaminants, including lead, mercury, pesticides, and forever chemicals like PFOA and PFOS. Compact and using durable metal hardware, it costs around $120 per year for filter replacements. The faucet is available in multiple finishes.

The A.O. Smith AO-US-200 matches the Aquasana AQ-5200 in quality, certifications, and design, but it’s sold only at Lowe’s and offers just a brushed nickel faucet. Replacement filters cost about $120 annually.

The Aquasana AQ-5300+ Max Flow offers the same top certifications as the AQ-5200 but with higher flow (0.72 vs. 0.5 GPM), larger capacity (800 vs. 500 gallons), and a sediment prefilter for sediment-rich water. It’s larger and costs more upfront and for filters ($160 annually).

The Aquasana Claryum Direct Connect installs easily without drilling, ideal for renters or those who can’t add a separate filter faucet. It offers top certifications and up to 1.5 GPM flow, with a 784-gallon (six-month) filter lifespan. However, it’s large (20.5 x 4.5 inches) and lacks a sediment prefilter, making it less suitable for sediment-heavy water or tight spaces.

Who this is for

For households using over 2–3 gallons of water daily, an under-sink filter is better than a pitcher, providing filtered water instantly for drinking and cooking. These systems have higher capacity (hundreds of gallons vs. 40) and longer lifespans (six months vs. two) and remove more contaminants. However, they cost more upfront, take up cabinet space, and require basic plumbing for installation, possibly needing a sink or countertop hole for the faucet.

How we picked

This guide focuses on cartridge-based under-sink filters, which are compact, easy to install, and certified to ANSI/NSF standards for top performance. We prioritized filters certified for chlorine, lead, VOCs, and emerging contaminants (401 standard), with a capacity of at least 500 gallons (six months of use). Cost, hardware quality, availability, and reviews also influenced our picks. While effective and durable, these filters require careful installation to avoid leaks, and additional precautions like a smart leak detector can provide extra security.

Our pick: Aquasana AQ-5200

We recommend the Aquasana AQ-5200 (Claryum Dual-Stage) for its top ANSI/NSF certifications, including chlorine, lead, mercury, VOCs, microplastics, and emerging contaminants like PFOA and PFOS. Its solid metal faucet and plumbing hardware, compact size, and strong value (around $140 upfront, $60 for replacement filters) make it a standout. The AQ-5200 effectively removes over 50 contaminants, including pesticides and industrial chemicals, making it a great choice for comprehensive water filtration.

The Aquasana AQ-5200 stands out with its superior certifications and advanced filter technologies, including catalytic carbon for chloramine and a 0.5-micron pore size for cryptosporidium and giardia. Its solid metal faucet and T-shaped plumbing fixture offer better durability than plastic alternatives, while compression fittings ensure a secure seal. Compact in design, it takes up less space than larger systems, making it ideal for small cabinets. With excellent reviews and a price of about $140 ($60 for replacement filters), it’s one of the best values for comprehensive filtration.

Flaws but not dealbreakers

The Aquasana AQ-5200 has a lower flow rate (0.5 gpm) and capacity (500 gallons) compared to some competitors, but its compact size compensates for these drawbacks. If you need higher flow or capacity, consider the AQ-5300+ (0.72 gpm, 800 gallons) or the Claryum Direct Connect (1.5 gpm, 784 gallons). The AQ-5200’s manual is somewhat unclear, but installation remains straightforward. Be cautious during installation to avoid leaks, and consider a smart leak detector. The system includes a separate faucet, but using your own faucet may void the NSF certification. For sediment-rich water, the AQ-5300 with a prefilter is a better choice.

Runner-up: A.O. Smith AO-US-200

The A.O. Smith AO-US-200 is nearly identical to the Aquasana AQ-5200, with the same certifications, compact size, filter technologies, and all-metal construction. It offers the same 0.5 gpm flow rate and 500-gallon capacity, and is priced similarly. The main differences are that it’s exclusive to Lowe’s and has a brushed-nickel faucet, while the AQ-5200 offers more faucet finishes. If you prefer brushed nickel, consider checking sales for potential savings.

The A.O. Smith AO-US-200 has similar manual issues as the Aquasana AQ-5200. Our unit also came with one 6-foot length of plastic tubing instead of the expected two 3-foot lengths, requiring owners to cut it themselves.

Upgrade pick: Aquasana AQ-5300+ Max Flow

The Aquasana AQ-5300+ Max Flow offers identical certifications to the AQ-5200 and A.O. Smith AO-US-200 but has a higher flow rate (0.72 gpm) and larger capacity (800 gallons). It also includes a sediment prefilter. However, it’s larger, more expensive upfront ($150), and costs more for replacement filters ($80). It retains the same six-month lifespan for filters as the others.

The AQ-5300+ Max Flow is significantly larger than the AQ-5200 and A.O. Smith filters (13 x 12 x 4 inches vs. 9 x 8 x 4 inches), requiring more cabinet space. It needs about 15 inches of vertical space and 13 inches of horizontal clearance for installation. Additionally, it features a Bluetooth-enabled performance indicating device (PID) that alerts you when it’s time to replace the filters, although we recommend setting a separate calendar reminder.

Also great: Aquasana Claryum Direct Connect

The Aquasana Claryum Direct Connect is ideal for renters or homes without a dedicated faucet mounting hole, as it connects directly to the cold-water line and sends filtered water to the main faucet. This design makes installation easier than other under-sink filters, which require a separate faucet and more complex mounting. It features the same exceptional ANSI/NSF certifications as other Aquasana models and reduces 77 contaminants, including lead, mercury, and PFOA/PFOS. The filter has a high flow rate of 1.5 gallons per minute, three times faster than the AQ-5200, and is rated for 784 gallons, or about six months of use.

Installation is straightforward, taking about 10 minutes with just an adjustable wrench and screwdriver. However, the filter is larger than others at 20½ inches long and 4½ inches wide, so ensure you have enough space. One downside is that the plastic adapter can be prone to cross-threading during installation, but taking care can avoid this. Despite this, reviews are generally positive, especially for its convenience and performance.