Clearly Filtered products are tested to NSF/ANSI standards but are not certified directly by NSF International. This is an important distinction that confuses many water filter shoppers. The company claims its filters are tested to NSF/ANSI standards 42, 53, 244, 401, and 473 at independent laboratories, but that is not the same as carrying official NSF certification.
Tested to NSF Standards vs. NSF Certified
NSF International is a nonprofit organization that develops testing standards for water filtration products and verifies that products meet them. When a product is “NSF certified,” it means NSF itself has tested and verified the filter’s performance, and the manufacturer submits to ongoing audits and retesting. The product earns the right to display the NSF certification mark.
“Tested to NSF standards” means something different. It means a third-party lab used the same testing protocols NSF developed, but NSF did not conduct or oversee the testing. Three main laboratory organizations are accredited by the American National Standards Institute (ANSI) to test products against NSF standards: NSF itself, the Water Quality Association (WQA), and IAPMO R&T. A product tested at any of these labs follows the same protocols, but only NSF-conducted testing results in an official NSF certification mark.
Clearly Filtered uses independent labs to test its filters against NSF/ANSI protocols. The company publishes its lab results, but you won’t find Clearly Filtered listed in NSF’s database of certified products. For some buyers this distinction matters a great deal; for others, the lab data itself is sufficient.
What the NSF/ANSI Standards Actually Cover
The standards Clearly Filtered references each target a different category of contaminants. NSF/ANSI 42 covers aesthetic issues like chlorine taste and odor. NSF/ANSI 53 addresses health-effect contaminants including lead, mercury, and volatile organic compounds. NSF/ANSI 401 targets emerging contaminants such as prescription drugs, over-the-counter medications, herbicides, pesticides, and other chemical compounds that show up in drinking water at trace levels. NSF/ANSI 473 specifically covers PFAS, the “forever chemicals” found in many water supplies.
Each standard has defined pass/fail thresholds. A filter tested to NSF/ANSI 53 for lead reduction, for example, must reduce lead to below the EPA action level under specific flow rates and water conditions. The testing protocols simulate real-world use, running contaminated water through the filter across its rated lifespan to confirm it still performs near the end of the filter’s life, not just when it’s brand new.
Clearly Filtered’s Contaminant Removal Claims
Clearly Filtered markets its water pitcher as capable of removing over 365 contaminants. The most notable claims include 100% removal of tested PFAS compounds, a figure that the Environmental Working Group independently verified in its guide to PFAS water filters. That puts the Clearly Filtered pitcher among the top-performing pitcher filters for forever chemicals specifically.
The company also claims high removal rates for lead, fluoride, chromium-6, and glyphosate (a common herbicide). These figures come from the company’s published lab reports rather than from NSF’s own certified product listings. If verification matters to you, downloading those lab reports from the Clearly Filtered website and checking which laboratory conducted the testing is worth the few minutes it takes. Look for a lab with ISO/IEC 17025 accreditation, which is the international standard for testing laboratory competence.
Filter Lifespan and Practical Details
The Clearly Filtered water pitcher filter is rated for 100 gallons before it needs replacement. For a household of two, that typically works out to roughly every three to four months depending on how much water you drink. The company notes that heavily contaminated water can reduce both filtration speed and lifespan, so you may need to replace filters more frequently if your local water quality is poor.
One thing to watch for: as any pitcher filter ages, flow rate slows. With Clearly Filtered, this slowdown is more noticeable than with simpler carbon-only pitchers because the filtration media is denser and targets a wider range of contaminants. A noticeably slower pour is actually a sign the filter is still working, not that it’s broken. When water barely passes through at all, it’s time to swap the filter.
How to Verify Any Filter’s Certification
If official NSF certification is important to you, NSF maintains a searchable public database at info.nsf.org where you can look up any product by brand name. Products that appear in that database have been tested, certified, and are subject to ongoing compliance monitoring by NSF itself. Products that don’t appear may still perform well, but they lack that specific layer of third-party oversight.
The Water Quality Association’s Gold Seal program and IAPMO R&T certification are both legitimate alternatives. All three organizations are ANSI-accredited and test to the same NSF/ANSI standards. A WQA Gold Seal or IAPMO certification carries comparable technical weight to NSF certification, even though NSF has the strongest name recognition among consumers. When evaluating any water filter, the key question isn’t just which lab tested it, but whether the testing covered the specific contaminants you’re concerned about in your local water supply.