out of 5
The best under-sink filter for people who don’t want reverse osmosis: certified for 78 contaminants including lead and PFAS, while keeping healthy minerals and wasting no water. The catch is filter cost, and the jobs only RO can do.
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The broad-spectrum filter that isn’t reverse osmosis
The Aquasana Claryum 3-Stage Max Flow is an under-sink carbon system, and it answers a specific question well: how do you remove a lot of contaminants without the downsides of reverse osmosis? It is WQA tested and certified to NSF/ANSI Standards 42, 53 and 401 to reduce 78 contaminants, including 99% of lead and microplastics, 97% of chlorine, and 96% of PFOA and PFOS. Crucially it does all that while retaining the beneficial minerals RO strips out, and it produces no wastewater at all. Add a genuinely fast 0.72 GPM flow with no tank to wait on, plus tool-free filter changes, and it is one of the easiest broad-spectrum filters to live with. See where it lands in our roundup of the best under-sink water filters.
Worth noting how unusual that certification is within this brand’s range. Aquasana’s Rhino whole-house filters are only independently tested, not listed on a certification register. The Claryum under-sink line genuinely is certified, and by an accredited third-party body, which is why this scores better with us on contaminant reduction than its bigger siblings.
The honest limits are two. First, it is a carbon filter, so it deliberately does not remove fluoride, total dissolved solids, arsenic, or nitrates, the jobs that need reverse osmosis. Second, its replacement cartridges are expensive, roughly $120 to $160 a year, which is the priciest part of ownership and higher than many RO systems cost to run. Judge it as a certified, mineral-keeping, no-waste alternative to RO for city water and it is excellent; expect it to match RO on everything and it will not.
Best for: city-water homes that want certified reduction of lead, PFAS, microplastics, chlorine and more at the tap, with the minerals kept, no wastewater and fast flow, and that don’t need to remove fluoride, TDS, or arsenic.
The model numbers have changed. Aquasana has replaced its AQ-5000-series Claryum systems with the AQ-6000 series. The Max Flow reviewed here is now the AQ-6300M, previously sold as the AQ-5300+. Filtration and certification are unchanged; if you find an AQ-5300+ still listed, it is older stock of the same system.
How it scored, category by category
Each category is weighted into the overall score. Its broad certified reduction and fast flow carry it; the high ongoing filter cost is what holds it back.
What it removes, and what it keeps
Every figure below comes from the Claryum line’s WQA certification to NSF/ANSI standards, an independent certification of the finished system. Unlike reverse osmosis, it is designed to leave beneficial minerals in the water, which is why some contaminants are intentionally out of scope.
| Contaminant | Reduction | Certified? |
|---|---|---|
| Lead | 99% | WQA / NSF 53 |
| Microplastics | 99% | WQA / NSF 401 |
| Chlorine & chloramine | 97% | WQA / NSF 42 |
| PFAS (PFOA / PFOS) | 96% | WQA / NSF 53 |
| Pharmaceuticals & pesticides | Reduced | WQA / NSF 401 |
| Cysts & asbestos | Reduced | WQA / NSF 53 |
| Beneficial minerals (Ca, Mg) | Kept | By design |
| Fluoride | No | Needs RO |
| TDS, arsenic, nitrates | No | Needs RO |
Source: Aquasana’s published certified-products data. The Claryum line is WQA tested and certified to NSF/ANSI Standards 42, 53 and 401 covering 78 contaminants. WQA is an accredited third-party certifier testing to the same NSF standards, though the product carries a WQA mark rather than an NSF one. It does not reduce fluoride, TDS, arsenic, or nitrates; for those you need reverse osmosis, see the iSpring RCC7AK or our fluoride guide.
Pros and cons
What we liked
- Genuinely certified: 78 contaminants including 99% lead and 96% PFAS
- Keeps beneficial minerals and produces no wastewater at all
- Fast 0.72 GPM flow with no tank wait; 800-gallon filter life
- Simpler to own than RO: no tank, no drain connection, no power
Worth considering
- High ongoing filter cost, roughly $120–$160 a year
- Doesn’t remove fluoride, TDS, arsenic, or nitrates (RO territory)
- Install drills a dedicated faucet hole; cartridges last ~6 months
- Costs more than the standard 3-Stage (AQ-6300) for the same certification
What actual owners report
Our score reflects certified performance. Owner sentiment, summarized from verified buyer and independent long-term reviews, shows a well-liked filter with one steady gripe.
Owners describe an immediate, noticeable jump in taste, and they like keeping the minerals and wasting no water. The complaint that comes up again and again is the cost of the replacement cartridges.
Owners consistently praise
- Big, immediate improvement in taste and smell
- No wastewater and water that still tastes “full,” not flat
- Fast flow and quick, tool-free filter changes
Common complaints
- Replacement cartridges are expensive over a year
- Install means drilling a hole for the dedicated faucet
- Occasional leaks at the fittings if not tightened well
Qualitative summary of recurring themes across verified buyer and independent long-term reviews, current as of August 2026. Note that Aquasana renumbered this line from AQ-5300+ to AQ-6300M, so review counts on the current listing understate the product’s track record. We report the patterns we see, positive and negative, and never cherry-pick.
The details
The current price is pulled live from Amazon.com and refreshes automatically. The system ships with the first set of filters, the dedicated faucet, and the parts needed for under-counter installation. Filter life varies with incoming water quality, and the ongoing cartridge cost is the single biggest factor in total cost of ownership, so weigh it against the lower running costs of a reverse-osmosis system before deciding.
Common questions
Is the Aquasana Claryum 3-Stage Max Flow certified?
Yes, genuinely. The Claryum line is WQA tested and certified to NSF/ANSI Standards 42, 53 and 401 to reduce 78 contaminants, including 99% of lead and microplastics, 97% of chlorine, and 96% of PFOA/PFOS. WQA is an accredited third-party certifier testing to the same NSF/ANSI standards, so these are verified reductions rather than marketing claims. Worth knowing this is not true of every Aquasana product: the Rhino whole-house line is independently tested rather than certified.
What happened to the AQ-5300+? Which model should I buy?
Aquasana renumbered the Claryum line: the AQ-5200 became the AQ-6200 (2-stage, 500 gallons), the AQ-5300 became the AQ-6300 (3-stage, 600 gallons), and the AQ-5300+ became the AQ-6300M Max Flow reviewed here (3-stage, 800 gallons, faster flow). The AQ-MF-1 Direct Connect attaches to your existing faucet with no plumbing or drilling, which makes it the one for renters. All share the same certification scope, so the choice is about flow rate, filter life and price rather than what gets removed. A.O. Smith also sells the identical Claryum technology as the AO-US-200.
Is the Max Flow worth it over the standard 3-Stage?
Only for flow and filter life. Both are certified for the same 78 contaminants with the same reduction figures. The Max Flow gives you noticeably faster water at the tap and 800 gallons per cartridge set against 600, which slightly lowers your cost per gallon. If you fill a lot of pots and bottles, it is worth the premium; if not, the standard AQ-6300 saves money up front.
Does it remove fluoride, arsenic, or TDS?
No. This is a carbon filter that intentionally keeps beneficial minerals, so it does not reduce fluoride, total dissolved solids, arsenic, or nitrates. Those require reverse osmosis, see the iSpring RCC7AK or our fluoride guide.
Claryum or a reverse-osmosis system?
Choose the Claryum if you want broad certified reduction, including lead and PFAS, while keeping minerals, with no wastewater, faster flow, and a simpler install. Choose RO if you also need fluoride, TDS, or arsenic removed, or want lower running costs. RO removes more but strips minerals, wastes some water, and needs a tank, though systems like the Home Master TMAFC-ERP add minerals back.
Should you buy it?
If you’re on city water and you want certified reduction of lead, PFAS, microplastics, chlorine and more at the kitchen tap, but you’d rather keep your minerals and skip reverse osmosis’s wastewater, slow flow, and tank, the Aquasana Claryum 3-Stage Max Flow is the best under-sink filter for the job. It is also one of the few products in Aquasana’s range with a genuine third-party certification behind it. Just budget for the cartridges. If you also need fluoride, TDS, or arsenic removed, or you want the lowest long-term running cost, a reverse-osmosis system like the iSpring RCC7AK or the no-install AquaTru Carafe is the better fit. For a broad-spectrum, mineral-keeping filter that isn’t RO, though, this Aquasana is the one to beat.
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