Data · Tested to vs certified to
Claimed vs certified
The single most useful thing we can show you: the gap between what a water filter markets and what it can actually prove. A claim is not a certification. "Tested to NSF standards" is a lab result a brand arranged once; an accredited NSF, WQA, or IAPMO certification is an audited program you can verify in a public registry. This table counts both, for every filter we score, and is computed from the same data behind the scorecards.
What the catalog shows
- 7 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.
- 18 of 25 hold at least one accredited certification. Holding one is the floor, not the finish line: scope matters, which is why the table shows the gap, not just a yes/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 claimed-minus-certified gap. A gap is not automatically dishonest - a brand may market a contaminant it genuinely reduces but never paid to certify. But on a site that scores proof, an uncertified claim earns no credit, and a large gap is a flag worth seeing.
How to read this
We only credit a contaminant on a scorecard when the certification is verifiable on the official NSF, WQA, or IAPMO database. Everything 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 score below one that certifies a handful. See our guide on tested to versus certified to.
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/