The Best Under-Sink Water Filters for 2026: Aquasana, Waterdrop and Reverse Osmosis Picks
By Claire Whitmore. Last updated October 2026.
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If your household drinks and cooks with more than a couple of gallons of filtered water a day, an under-sink system beats a pitcher. It uses your water pressure to filter on demand, so you can fill a pasta pot in a few minutes. It also removes a much wider range of contaminants than most pitchers, including lead and the forever chemicals PFOA and PFOS.
Our picks are based mainly on Wirecutter’s June 2026 guide. Its author has tested water filters since 2016 and checks every claim against the public NSF/ANSI certification databases. We also used Wirecutter’s reverse-osmosis guide, TechGearLab’s lab scores, Bob Vila’s hands-on install, and Consumer Reports’ flow and clogging tests. We haven’t tested these systems ourselves. Prices fluctuate, and Aquasana’s especially so.
Quick answer: the Aquasana Claryum 3-Stage Max Flow is the best under-sink filter for most homes. It carries 78 NSF/ANSI certifications, including lead and PFAS, and has a sediment pre-filter that prevents clogging. Renters and anyone who can’t add a faucet should get the Claryum Direct Connect. If you want reverse osmosis’s near-total removal, look at the tankless Waterdrop G3P600 or Wirecutter’s tank-based pick, Cloud RO.
Our picks at a glance
| Pick | Type | Best for | Approx. price* |
|---|---|---|---|
| Aquasana Claryum 3-Stage Max Flow | Carbon, separate faucet | Best overall | About $225 to $450 |
| Aquasana Claryum 2-Stage / A.O. Smith AO-US-200 | Carbon, separate faucet | Compact, clear water | About $119 to $125 |
| Aquasana Claryum Direct Connect | Carbon, existing faucet | Renters, no drilling | About $125 |
| Waterdrop G3P600 | Tankless reverse osmosis | Maximum removal | About $539 list |
| Cloud RO | Tank reverse osmosis | Certified RO with a small footprint | Varies |
*Prices from Wirecutter and TechGearLab at the time of writing. Aquasana prices swing a lot, so watch for sales.
The best under-sink water filters
1. Aquasana Claryum 3-Stage Max Flow: best overall
Best for: most households, especially in older homes with rusty pipes.
Wirecutter’s top pick is certified to NSF/ANSI standards for 78 contaminants, the joint-most of any filter it has reviewed. The list includes chlorine, chloramine, lead, mercury, total VOCs, multiple pesticides, microplastics, emerging contaminants and PFOA/PFOS. Its sediment pre-filter is the deciding feature. Wirecutter now considers clogging the most common way under-sink filters fail, and a pre-filter keeps the carbon and ion-exchange stages working far longer.
It delivers 0.72 gallons per minute, about 30% faster than most under-sink filters, and its filters are rated for 800 gallons. A replacement set costs about $90 and typically lasts six months to a year. A sensor measures actual use instead of guessing on a timer. The hardware is solid metal with compression fittings, and the included faucet comes in several finishes. It’s bulky, though: the housing measures 13 by 12 by 4 inches, and it needs a separate faucet hole.
Pros
- 78 NSF/ANSI certifications, including lead and PFAS
- Sediment pre-filter
- Faster flow
- Metal fittings and faucet
Cons
- Takes a lot of cabinet space
- Needs a countertop or sink hole
- Install carefully to avoid leaks
2. Aquasana Claryum 2-Stage (or A.O. Smith AO-US-200): best compact option
Best for: homes with clear, sediment-free water and smaller cabinets.
The 2-Stage has the same 78 certifications in a much smaller 9-by-8-by-4-inch housing. It costs less to buy, and filters run about $75 a set. The catch is that there’s no pre-filter, the flow is 0.5 gallons per minute and the filters are rated for 500 gallons. Wirecutter recommends it only if your water never runs cloudy or brown.
The A.O. Smith AO-US-200 is the identical system under the parent company’s name. It’s usually $10 to $25 cheaper, and the only difference is that its faucet comes only in brushed nickel.
Pros
- Same certifications as our top pick
- Compact
- Cheaper filters
Cons
- No pre-filter
- Slower flow
- Shorter filter life
3. Aquasana Claryum Direct Connect: best for renters
Best for: sinks with no spare hole, or anyone who can’t drill.
This system connects to your cold-water line and sends filtered water through your existing faucet, so there’s nothing to drill. It can even lie on the cabinet floor. It has the same NSF/ANSI certifications as the other Aquasana picks, a claimed flow of up to 1.5 gallons per minute (twice the 3-Stage’s), and a 784-gallon filter.
Since all your cold water is filtered, filters run out sooner, and they cost about $90. There’s also no pre-filter, and Wirecutter’s test unit clogged immediately when a burst of rust came through the pipes.
Pros
- No drilling
- Uses your existing faucet
- High flow
Cons
- Filters every cold-water use, so filters wear faster
- Clogs with sediment
4. Waterdrop G3P600: best reverse osmosis
Best for: owners who want the broadest contaminant removal and plenty of filtered water.
TechGearLab rates the tankless G3P600 95 out of 100, its best water filter overall, with near-perfect scores for PFAS (10), microplastics (10) and lead and metals (9.8). An electric pump means unlimited on-demand water without a storage tank, and it wastes far less water than older RO systems, about 1 gallon of wastewater for every 2 gallons filtered. Filter changes are a simple twist and pull.
Bob Vila’s testers said they were “genuinely shocked at how great the water tasted” and liked the faucet’s live TDS display, though installation took about two hours, including drilling the sink and reaching an outlet. Annual filter costs run about $145, and you may need a plumber or electrician.
Pros
- Best-in-class removal
- Tankless, saves space
- Low wastewater for RO
- Easy filter swaps
Cons
- Expensive
- Needs an outlet and drilling
- Removes minerals some people like
5. Cloud RO: best tank-based reverse osmosis
Best for: those who prefer a certified, non-electric RO system.
Wirecutter’s top reverse-osmosis pick is a tank-based system that uses your pipe pressure to fill a self-pressurizing reservoir. It’s NSF/ANSI 58 certified and third-party tested for lead, mercury, arsenic, PFOA/PFOS and VOCs. Wirecutter says its design saves more cabinet space than typical tank systems. Tankless pump systems get more buzz, but tank systems don’t need power and have fewer parts to fail.
Pros
- NSF 58 certified
- No electricity needed
- Compact for a tank system
Cons
- Tank still takes space
- Slower refill than tankless
Carbon filter or reverse osmosis?
Carbon and ion-exchange systems like the Aquasana picks remove the contaminants most people worry about, including chlorine taste, lead, PFAS, VOCs and microplastics, while leaving minerals in. They’re cheaper, easy to install yourself, and waste no water.
Reverse osmosis pushes water through a membrane fine enough to remove dissolved solids, fluoride, nitrates and arsenic too. It costs more, sends some water down the drain, often needs power, and strips minerals, so some systems add them back. Choose RO if a water test shows contaminants that carbon can’t handle, or if you simply want the most thorough filtration.
How to choose an under-sink filter
- Test your water first. Wirecutter recommends a test before you buy. You may need much less filter than you think, or something carbon can’t handle.
- Insist on real certification. Look for the word “certified” to an NSF/ANSI standard and a named lab (NSF, WQA or IAPMO). “Tested to” isn’t the same thing. Wirecutter found popular brands like iSpring, APEC and Frizzlife lacked certification for the filters it checked.
- Minimum certifications. Wirecutter’s bar is chlorine, lead, total VOCs and at least one PFAS, ideally plus NSF/ANSI 401 for emerging contaminants.
- Pre-filter. Essential in older homes with rusty pipes.
- Faucet and space. Measure your cabinet and check for a free hole: a soap dispenser, side sprayer or knockout. Otherwise choose the Direct Connect.
- Running costs. Budget $75 to $150 or more a year for filters.
Installation and leak protection
Most carbon systems are a DIY job of an hour or two. Wirecutter warns that under-sink filters occasionally leak or fail outright, and that can cause serious water damage. Don’t cross-thread connectors, don’t over-tighten filter housings, and check for drips over the first few days. A smart leak detector under the sink, or a smart shutoff valve, is cheap insurance.
FAQ
Do under-sink filters remove PFAS?
Certified ones do. All of the Aquasana picks are NSF/ANSI certified for PFOA and PFOS, and reverse-osmosis systems like the Waterdrop G3P600 scored a perfect 10 for PFAS removal in TechGearLab’s tests.
How often do I replace filters?
Typically every six to 12 months, depending on capacity and use. The Claryum 3-Stage is rated for 800 gallons, and its sensor beeps when it’s time.
Is an under-sink filter better than a fridge filter?
Usually, yes. Fridge filters are smaller and often certified for fewer contaminants. An under-sink system with its own faucet also serves your cooking water.
Can I install one myself?
Carbon systems, yes, if you’re comfortable with basic plumbing. Reverse-osmosis systems may need drilling, a drain connection and an outlet, so some people hire a plumber.
The bottom line
The Aquasana Claryum 3-Stage Max Flow is the under-sink filter to buy. It has top-tier certifications, a pre-filter that prevents clogging, quick flow and quality hardware. Pick the Claryum Direct Connect if you can’t drill, and the Waterdrop G3P600 or Cloud RO if you want the most thorough reverse-osmosis filtration.
