Data · Tested to vs certified to
Claimed vs certified
Of the 25 water filters we score, 9 market a contaminant-reduction claim while holding no accredited NSF, WQA, or IAPMO certification, and 11 market lead or PFAS reduction they are not certified for. A claim is not a certification.
If you are deciding which filter to trust, here is the one gap that matters: what a brand markets versus what it can actually prove. The two are not the same. "Tested to NSF standards" is just a lab result a brand paid for once. An accredited certification - from NSF, WQA, or IAPMO, the three independent bodies that audit filters - is an ongoing program you can look up yourself in a public registry. The table below counts both for every filter we score, drawn from the same data behind the scorecards. The wider the gap, the more a brand is asking you to take on faith.
What the catalog shows
- 9 of 25 scored water filters make contaminant-reduction claims while holding zero accredited certification - pure "tested to," not "certified to."
- 11 market lead or PFAS reduction they are not certified for - the two contaminants people most want removed.
- 16 of 25 hold at least one accredited certification. Treat that as the floor to clear, not a gold star - what a filter is certified to reduce matters more than whether it holds any cert at all, which is why the table shows you the gap rather than a simple yes or no.
- Widest gap: the Clearly Filtered 3-Stage Under-Sink markets 13 contaminants and is certified for 0.
Every scored water filter, by gap
Sorted by the widest gap between what a filter claims and what it is certified for. A gap is not proof of dishonesty - a brand may genuinely reduce a contaminant it simply never paid to certify. But since we score proof, an uncertified claim earns no credit, and a wide gap is something you want to see before you buy.
How to read this
We credit a contaminant on a scorecard only when you can verify the certification yourself on the official NSF, WQA, or IAPMO database. Anything a brand lists beyond that - lab tests it commissioned, "tested to" language, marketing copy - counts as a claim, not a certification, and earns no points. That is why a filter advertising hundreds of contaminants can land below one that certifies a handful: you are paying for what is proven, not what is printed on the box. If the "tested to" versus "certified to" distinction is new to you, our guide on tested to versus certified to walks through it.
Cite this analysis
Figures are computed across every scored water filter and update as the catalog grows. Cite with attribution to FilterScored and a link to this page.
FilterScored. "Claimed vs Certified: Which Water Filters Market What They Cannot Prove." https://www.filterscored.com/reports/claimed-vs-certified/