The Aquasana OptimH2O is an under-sink reverse osmosis system certified under NSF/ANSI 58 and 401, with WQA third-party testing confirming reduction of PFAS (PFOA/PFOS), fluoride, arsenic, and lead. What sets it apart from many RO systems is the built-in Claryum remineralization stage, which adds calcium, magnesium, and potassium back into the water after filtration - addressing the flat taste that pure RO water is often criticized for. Trade-offs are typical of the RO category: some water goes to drain during filtration, the under-sink tank takes up cabinet space, and running costs are higher than carbon-only systems. For households that want certified PFAS reduction at the tap along with better-tasting remineralized water, it's a strong Mid-tier choice.
- WQA + 3 NSF certifications (58, 401, 473)
- Remineralization - better taste & pH
- NSF 401 covers pharmaceuticals & hormones
- NSF 473 specifically covers PFOA/PFOS
- Higher running cost than APEC
- Higher upfront price than APEC
- Requires dedicated faucet (drill needed)
What is the Aquasana OptimH2O
The OptimH2O is an under-sink reverse osmosis system that pairs a semi-permeable RO membrane with Aquasana's Claryum filtration technology across multiple stages, then adds a dedicated remineralization stage before the water reaches the faucet. Reverse osmosis on its own strips out dissolved minerals along with contaminants, which is part of why RO water can taste flat - the remineralization stage is designed to add calcium, magnesium, and potassium back in after filtration, without reintroducing the contaminants that were removed.
Like most residential RO systems, it installs under the kitchen sink alongside a dedicated faucet and a storage tank, with a drain-line connection for the reject water stream - confirm current tank size and drain ratio specs on Aquasana's product page before purchase, since manufacturers periodically update hardware revisions.
NSF certification - what's verified
The OptimH2O carries NSF/ANSI 58 certification, the core standard for reverse osmosis systems that verifies reduction of total dissolved solids and specific contaminants across the membrane. It also carries NSF/ANSI 401, which covers reduction of "emerging compounds" - a category that includes certain pharmaceuticals, herbicides, and pesticides not covered by older standards. Independent WQA (Water Quality Association) testing supports reduction of PFAS (PFOA/PFOS), fluoride, arsenic, and lead specifically.
One correction worth flagging for anyone researching Aquasana's under-sink RO lineup: some older marketing material and third-party articles reference an "NSF P473" certification. NSF P473 was a protocol standard that has since been absorbed into NSF/ANSI 53 and 58 - it is no longer a standalone, current certification. When evaluating this system (or any RO system), look for NSF 58 and 401 specifically rather than P473.
What it removes
Based on its NSF certifications and WQA testing, the OptimH2O is verified to reduce PFAS (PFOA/PFOS), fluoride, arsenic, and lead, along with the broader range of contaminants typically addressed by RO membranes - dissolved solids, chlorine and chloramine taste/odor (via the pre-filter carbon stages), and a range of emerging compounds under NSF 401. The Claryum remineralization stage then reintroduces beneficial minerals, which is a meaningful differentiator versus RO systems that produce demineralized water only.
Installation and maintenance
As an under-sink system, installation involves connecting to the cold-water supply line, mounting a dedicated faucet (which typically requires drilling a hole in the sink or counter if one isn't already present), and running a drain-line saddle valve. Many homeowners comfortable with basic plumbing install it themselves in an afternoon, though professional installation is recommended if you're unsure about drilling through stone or solid-surface countertops. Ongoing maintenance involves periodic filter and membrane replacement - check Aquasana's current recommended replacement schedule, as this varies by filtration stage.
Who it's for
The OptimH2O is best suited to households that want certified PFAS, fluoride, arsenic, and lead reduction specifically at the kitchen tap, and who care about drinking-water taste enough to value the remineralization step over a standard strip-and-serve RO system. It's less suited to renters who can't modify plumbing, or households wanting whole-house treatment - for point-of-entry protection at every tap, see our Aquasana Rhino EQ-1000 review instead.
OptimH2O vs Waterdrop G3P600 vs APEC ROES-50
| Feature | Aquasana OptimH2O | Waterdrop G3P600 | APEC ROES-50 |
|---|---|---|---|
| Price tier | Mid | Premium | Budget |
| NSF certs | 58, 401 (WQA-tested PFAS) | 58, 42, 372 | 58, WQA |
| Remineralization | Claryum (Ca, Mg, K) | No | No |
| Tank | Standard under-sink tank | Tankless | 3.2 gal tank |
| PFAS tested | WQA | SGS | Not specifically certified |
| Best for | Taste + verified PFAS/fluoride/arsenic removal | Space-saving, high flow rate | Lowest-cost certified RO |
Choose Waterdrop G3P600 if: under-sink space is limited and you want a tankless design with a faster flow rate - see our full Waterdrop G3P600 review.
Choose APEC ROES-50 if: budget is the top priority and you don't need remineralization - see our full APEC ROES-50 review.
Choose the OptimH2O if: you want independently WQA-tested PFAS, fluoride, and arsenic reduction plus better-tasting remineralized water, and you're comfortable with a standard under-sink tank.