Compare Under Sink Water Filter
Clearly Filtered 3-Stage Under-the-Sink Water Filtration System scores higher on safety - here's why.
R3 scored the Aquasana OptimH2O Reverse Osmosis + Claryum Under Counter Water Filter System 9.0/10 and the Clearly Filtered 3-Stage Under-the-Sink Water Filtration System 10.0/10 on the same under sink water filter scoring system, weighing safety, efficacy, and usability. The Clearly Filtered 3-Stage Under-the-Sink Water Filtration System comes out ahead.
The most important dimensions, side by side.
See which one actually scores higher — and why
Free account unlocks full safety scores, spec-by-spec breakdown, and the R3 verdict on Aquasana OptimH2O Reverse Osmosis + Claryum Under Counter Water Filter System vs Clearly Filtered 3-Stage Under-the-Sink Water Filtration System.
Unlock the full Aquasana OptimH2O Reverse Osmosis + Claryum Under Counter Water Filter System vs Clearly Filtered 3-Stage Under-the-Sink Water Filtration System breakdown
Free account unlocks all safety scores, complete spec comparison, scoring rationale, and the R3 verdict on which one to buy.
Everything you need to make the call - who each one is for, and who should skip it.
Go for it if you...
You need NSF P473 — the PFAS-specific certification — combined with NSF 53 lead coverage, NSF 401 emerging contaminants, and NSF 58 comprehensive RO in a single under-sink system.
You want full test transparency: Aquasana's certified products page lets you verify every contaminant claim before you buy.
You're comfortable with semi-annual filter replacements and building that maintenance habit in exchange for the deepest certification profile in the category.
Your household water has documented PFAS, lead, chloramine, or emerging contaminant concerns that require formal NSF certification to address.
You want the most rigorously documented PFAS and contaminant protection available in an under-sink filter and are willing to invest in it
You live in a rental or don't want to drill a new faucet hole — the inline installation works with your existing setup
You want zero water waste and don't need a reverse osmosis system to feel confident in your water quality
The main thing to know
The OptimH2O's Exceptional rating comes from its certification depth, not its maintenance convenience. NSF P473 — the PFAS-specific standard — plus four other NSF certifications is the broadest certified coverage in this category. The honest tradeoff is the pre-filter: 365 gallons means roughly twice-yearly replacements at roughly $211 per year. That's the real cost of this system's certification breadth. If that schedule fits your routine, the safety credentials are the strongest available in a DIY under-sink format.
At $495 upfront, this is one of the more expensive under-sink filters on the market — but the filter replacements are annual at the 2,000-gallon life, and no competing filter matches the combination of NSF 473 PFAS certification, 232-contaminant independent verification, and no-drill installation.
Skip this if you...
Frequent filter changes feel unmanageable — at standard household usage the pre-filter needs replacing every 6 months.
You're optimizing for low annual running cost — roughly $211 per year in filter replacements is above average for an under-sink system.
You want a simple install without drilling a new hole — the dedicated faucet requires a new hole in your sink deck or counter.
You're on a tight budget and need a more affordable entry point — consider the Clearly Filtered pitcher while saving up
You need a guaranteed published flow rate because multiple family members will be drawing filtered water simultaneously
You prefer reverse osmosis technology specifically and don't mind the installation complexity it requires
Neither of these quite what you're looking for?
I've reviewed all Under Sink Water Filter options at every price pointEvery Under Sink Water Filter in our database is scored using R3's deterministic scoring system - the same inputs always produce the same score. For this comparison, we evaluated Aquasana and Clearly Filtered across 3 independent criteria: Safety (68%), Efficacy (31%), Usability (1%). No sponsored rankings. No paid placements.
Straight answers - no sponsored content, no filler.
I'd start with Clearly Filtered Clearly Filtered 3-Stage Under-the-Sink Water Filtration System - it scored 10.0/10 overall in our scoring system. Safety is our top-weighted scoring pillar, followed by efficacy, and usability. Check which pillar matters most to your family and compare those specific scores.
R3 uses a deterministic scoring system - the same inputs always produce the same score. We evaluate each Under Sink Water Filter across Safety, Efficacy, Usability using independently verified data. No sponsored rankings. No paid placements. Every score is fully reproducible.
Not necessarily. The overall score reflects how we weight those three pillars, but your priorities may differ. If you care most about safety, compare the safety scores directly. If budget drives your decision, the prices tell a clearer story. The "right" pick is the one that matches what matters most to your family.
Not the right match? Explore these alternatives in the same category.
Hydroviv
Hydroviv Under Sink Water Filter
3.5
Clearly Filtered
Clearly Filtered 3-Stage Under-the-Sink Water Filtration System
10.0
Aquasana
Aquasana Claryum 2-Stage Under Counter Water Filter System AQ-5200
9.3
APEC Water Systems
APEC Water Systems ROES-50 Reverse Osmosis Drinking Water Filter System
8.9
