# NSF/ANSI 53 (Drinking Water Treatment Units - Health Effects) > The U.S. standard that certifies water filters for reduction of contaminants with a health effect - lead, certain VOCs, cysts, and some PFAS. It is the certification families should look for on a pitcher, faucet-mount, or under-sink filter when the concern is what is harmful in the water, not just taste. Certification is contaminant-specific, so the named contaminant list matters as much as the standard number. **Type:** standards **Categories:** water-filter, pitcher-water-filters, countertop-water-filter, under-sink-water-filter, faucet-mounted-water-filter **Source:** https://www.r3recs.com/learn/standards/nsf-ansi-53 ## Overview Walk down the water-filter aisle and almost every box has an "NSF certified" badge on it. The badge alone does not tell you much, because NSF International certifies water filters against three different standards that test for completely different things. When the concern is what is actually *harmful* in the water, the standard that matters is **NSF/ANSI 53: Drinking Water Treatment Units - Health Effects**. NSF/ANSI 53 is the U.S. consensus standard for certifying that a point-of-use water filter (a pitcher, a faucet-mount, an under-sink unit, a countertop system) reduces specific contaminants that have a recognized adverse health effect. It is jointly maintained by NSF and ANSI (American National Standards Institute) and is referenced by regulators and retailers across the country. ## What NSF/ANSI 53 actually certifies The standard is built around contaminants with a *health* effect, as opposed to contaminants that only affect taste, odor, or appearance. The contaminants a filter can be certified to reduce under NSF/ANSI 53 include: - **Lead** - the headline contaminant for most families, especially anyone mixing infant formula - **Certain volatile organic compounds (VOCs)** - industrial and agricultural chemicals - **Cysts** - chlorine-resistant parasites such as *Cryptosporidium* and *Giardia* - **Chromium** (hexavalent and trivalent) - **Select per- and polyfluoroalkyl substances** - some certifications cover reduction of [PFAS](/learn/ingredients/pfas) compounds such as PFOA and PFOS - Other health-effect contaminants including MTBE, asbestos, and turbidity The single most important thing to understand about NSF/ANSI 53 is that it is **contaminant-specific**. A filter is never just "NSF/ANSI 53 certified" in the abstract. It is certified to reduce *particular* contaminants. A pitcher certified for lead and cysts may not be certified for VOCs or PFAS. Always read which contaminants the certification names, not just the standard number. ## How the lead test works (and why the numbers matter) The lead certification is where NSF/ANSI 53 earns its credibility, because the test is deliberately punishing. To pass, a filter is run with challenge water that has been dosed with **150 parts per billion (ppb) of lead** - about ten times the U.S. Environmental Protection Agency's action level of **15 ppb**. The filter has to bring that heavily contaminated water down below a strict limit, across the full rated life of the cartridge, not just when it is brand new. NSF tightened that limit. The pass mark for new lead certifications under NSF/ANSI 53 (and the reverse-osmosis standard NSF/ANSI 58) was lowered to **5 ppb**, down from the previous 10 ppb. So a newly certified filter has to reduce that 150 ppb challenge water to 5 ppb or below to carry the lead claim. This matters because, as the EPA notes, there is no known safe level of lead exposure for children, and lead usually enters tap water not at the treatment plant but from corroding pipes and fixtures inside the home. A filter with NSF/ANSI 53 lead certification is the one practical way to know that what comes out of the faucet has been independently verified, rather than trusting a marketing claim. ## NSF/ANSI 53 vs 42 vs 58 - the three you will see Most of the confusion in the parenting community comes from treating "NSF certified" as one thing. For water filters there are three distinct standards: - **NSF/ANSI 42 - Aesthetic Effects.** Certifies reduction of things that affect taste and smell, primarily chlorine, plus particulates. A filter certified *only* to NSF/ANSI 42 makes water taste better but is **not** verified to remove lead or other health contaminants. - **NSF/ANSI 53 - Health Effects.** The health-contaminant standard described here: lead, VOCs, cysts, some PFAS. - **NSF/ANSI 58 - Reverse Osmosis Systems.** Certifies reverse-osmosis systems for broad-spectrum reduction of dissolved contaminants, including arsenic, nitrates, fluoride, and PFAS. A good way to read a spec sheet: if you care about taste, NSF/ANSI 42 is enough. If you care about lead and other health contaminants, you need NSF/ANSI 53 (or 58 for an RO system). Many quality filters carry 42 and 53 together. ## PFAS and NSF/ANSI 53 Families researching "forever chemicals" should know that **some** NSF/ANSI 53 certifications now cover reduction of specific PFAS compounds, principally the long-chain PFOA and PFOS, measured against health-based thresholds. Not every NSF/ANSI 53 filter is certified for PFAS, so this is exactly the case where reading the named contaminant list matters. For the broadest PFAS reduction, a reverse-osmosis system certified to NSF/ANSI 58 with an explicit PFAS claim is generally the stronger option. ## How to verify a certification NSF maintains a free public database at listings.nsf.org. Search by manufacturer or product, and confirm two things: that the specific model appears, and that the contaminants you care about (for example, lead) are named in its NSF/ANSI 53 listing. Certification is model-specific, so search the exact product, not just the brand. Be alert to soft language. "Tested to NSF standards" or "meets NSF/ANSI 53" is **not** the same as being NSF certified, which requires independent testing, a facility audit, ongoing surveillance, and a listing in the database. If a product claims certification but you cannot find it in the database, treat that as a flag worth resolving with the manufacturer before you rely on it. ## The bottom line for families NSF/ANSI 53 is the certification to look for when the question is "does this filter actually remove what is harmful," not just "does it make the water taste better." The lead test in particular is rigorous and independently verified. The two habits that make the standard useful in practice: read which contaminants a filter is certified for (the standard number alone is not enough), and verify the listing at listings.nsf.org before you buy. ## Also Known As - NSF 53 - ANSI/NSF 53 - NSF/ANSI/CAN 53 - Drinking Water Treatment Units - Health Effects ## Where Found - Pitcher water filters (lead and cyst certifications) - Faucet-mounted water filters - Under-sink water filter systems - Countertop water filters - Refrigerator water filter cartridges - Reverse-osmosis systems (alongside NSF/ANSI 58) ## Label Guide **Look for:** - NSF/ANSI 53 certified for lead reduction - the claim that matters most for families and formula - NSF/ANSI 53 certified for cyst reduction - covers Cryptosporidium and Giardia - NSF/ANSI 42 and 53 together - taste plus health contaminants - Named contaminant list in the NSF listing - confirms exactly what the filter is certified to reduce - Listed at listings.nsf.org under the specific model number **Avoid / misleading:** - Tested to NSF standards or meets NSF/ANSI 53 without a certification listing - not the same as certified - NSF certified with no standard number - ask whether it is 42 (taste only), 53 (health), or 58 (reverse osmosis) - Reduces lead with no NSF/ANSI 53 certification to back the claim - unverified marketing - Filter-branded PFAS-free without PFAS named in the NSF/ANSI 53 or 58 listing ## How To Verify Search the free NSF certification database at listings.nsf.org by manufacturer or product model. Confirm the exact model is listed under NSF/ANSI 53 and that the contaminants you care about (for example, lead or cysts) are named in that listing. Certification is model-specific, so search the specific product, not just the brand. NSF can be reached at 1-800-NSF-MARK to confirm a claim. ## What This Does Not Cover NSF/ANSI 53 does not certify taste and odor improvement on its own - that is NSF/ANSI 42. It does not certify the broad-spectrum removal of a reverse-osmosis system - that is NSF/ANSI 58. It does not cover food equipment materials or cookware coatings - that is NSF/ANSI 51. And because it is contaminant-specific, a NSF/ANSI 53 certification for one contaminant (such as lead) does not imply reduction of any other contaminant the product does not name. ## R3 Bottom Line - NSF/ANSI 53 is the water-filter certification to look for when your concern is health contaminants - lead, VOCs, cysts, and some PFAS - rather than just taste, which is NSF/ANSI 42 - It is contaminant-specific: a filter is certified to reduce particular named contaminants, so read the contaminant list, not just the standard number - The lead test is rigorous - filters are challenged with water dosed at 150 ppb of lead (about 10x the EPA's 15 ppb action level) and must reduce it below a strict limit, lowered to 5 ppb for new certifications, across the cartridge's full life - For broad PFAS reduction, a reverse-osmosis system certified to NSF/ANSI 58 with an explicit PFAS claim is generally stronger than relying on a NSF/ANSI 53 filter - Verify any claim at listings.nsf.org by the specific model - 'tested to NSF standards' is not the same as being NSF certified and listed ## FAQ ### What does NSF/ANSI 53 mean on a water filter? It means the filter has been independently tested and certified by NSF to reduce specific contaminants that have a recognized health effect, such as lead, certain VOCs, cysts, and in some cases [PFAS](/learn/ingredients/pfas). It is the health-contaminant standard, as opposed to NSF/ANSI 42, which only covers taste and odor. Certification is contaminant-specific, so check which contaminants the listing names. ### Is NSF/ANSI 53 the standard I want for lead? Yes. NSF/ANSI 53 is the certification to look for if your concern is lead, including for mixing infant formula. To earn the lead claim, a filter is tested against challenge water dosed at 150 ppb of lead, roughly ten times the EPA's 15 ppb action level, and must reduce it below a strict limit (lowered to 5 ppb for new certifications) across the cartridge's full rated life. ### What is the difference between NSF/ANSI 42 and 53? NSF/ANSI 42 covers aesthetic effects, mainly chlorine taste and odor plus particulates. NSF/ANSI 53 covers health effects, such as lead, VOCs, and cysts. A filter certified only to NSF/ANSI 42 improves taste but is not verified to remove lead. Many good filters carry both 42 and 53. ### Does NSF/ANSI 53 cover PFAS? Some NSF/ANSI 53 certifications cover reduction of specific PFAS compounds, principally the long-chain PFOA and PFOS, but not all do. Because the standard is contaminant-specific, you have to confirm PFAS is named in the product listing. For the broadest PFAS reduction, a reverse-osmosis system certified to NSF/ANSI 58 with an explicit PFAS claim is usually the stronger choice. ### How do I verify a filter is really NSF/ANSI 53 certified? Search the free public NSF database at listings.nsf.org by product or manufacturer, and confirm the specific model is listed and names the contaminants you care about. Certification is model-specific, not brand-wide. Note that 'tested to NSF standards' on a box is not the same as being certified and listed. ### Is NSF/ANSI 53 required by law? No. It is a voluntary consensus standard. Manufacturers choose to submit products for independent certification, which includes laboratory testing, facility audits, and ongoing surveillance. Because it is voluntary, an uncertified filter is not necessarily unsafe, but a certified one has been independently verified rather than self-declared. ### Does NSF/ANSI 53 apply to shower or whole-house filters? NSF/ANSI 53 is written for drinking-water treatment units that reduce health-effect contaminants. Point-of-use drinking filters (pitchers, faucet-mount, under-sink, countertop) are where you will most often see it. Shower and whole-house systems may carry different NSF certifications or none, so check the specific product listing rather than assuming the standard applies. ## Sources - [NSF/ANSI 42, 53 and 401: Filtration Systems Standards](https://www.nsf.org/knowledge-library/nsf-ansi-42-53-and-401-filtration-systems-standards) — *NSF International* (2024) - [Lead in Drinking Water](https://www.nsf.org/consumer-resources/articles/lead-drinking-water) — *NSF International* (2024) - [Drinking Water Treatment Units Must Now Meet Stricter Requirements for Lead Reduction Certification](https://www.nsf.org/news/drinking-water-treatment-units-stricter-requirements-lead-reduction-cert) — *NSF International* (2023) - [Basic Information about Lead in Drinking Water](https://www.epa.gov/ground-water-and-drinking-water/basic-information-about-lead-drinking-water) — *U.S. EPA* (2024) --- Source: https://www.r3recs.com/learn/standards/nsf-ansi-53 Methodology: https://www.r3recs.com/methodology/how-we-score-products