NSF 42 vs 53 vs 58 vs 401
"NSF certified" is nearly meaningless without the standard number. 42 = taste and odor only. 53 = the health tier (lead, mercury, chromium-6, VOCs). 58 = reverse-osmosis systems. 401 = emerging contaminants (pharmaceuticals, microplastics). 44 = water softeners (hardness). 372 = lead-free materials (not contaminant reduction). If you want lead removed, you're looking for 53 or 58 — not 42, and not 372 alone.
The one thing to know: The word 'certified' matters less than the NSF/ANSI standard NUMBER behind it. NSF/ANSI 42 covers aesthetics only (chlorine taste and odor); 53 is the health tier (lead, cadmium, mercury, VOCs, chromium-6); 58 covers reverse-osmosis systems; and 401 covers emerging contaminants like pharmaceuticals and microplastics. A filter 'NSF certified' under 42 does nothing certified for lead — so always read the number, not just the badge.
The standards, decoded
| Standard | What it certifies | Removes lead? |
|---|---|---|
| NSF/ANSI 42 | Aesthetics — chlorine taste & odor, some particulates | No |
| NSF/ANSI 53 | Health effects — lead, cadmium, mercury, chromium-6, VOCs | Yes (certified) |
| NSF/ANSI 58 | Reverse-osmosis systems — TDS + a list of contaminants | Yes (via RO) |
| NSF/ANSI 401 | Emerging contaminants — pharmaceuticals, microplastics, some pesticides | Often paired with 53 |
| NSF/ANSI 44 | Cation-exchange water softeners — hardness reduction | N/A (softens) |
| NSF/ANSI 372 | Lead-free materials of the device itself | No — materials only |
The trap: "NSF certified" with no number
The most common move in water-filter marketing is to say "NSF certified" while the actual certification is only NSF 42 (taste) or NSF 372 (lead-free materials) — leaving the buyer to assume it removes lead or PFAS. It doesn't. A pitcher certified to 42 and a pitcher certified to 53 can look identical on the shelf and cost nearly the same, but only one is verified to reduce lead. Read the number every time.
What about PFAS?
PFAS ("forever chemicals," including PFOA/PFOS) reduction is certified under specific scopes of NSF/ANSI 53 and 58 (and the older P473 protocol). Many products claim PFAS reduction based on their own lab testing without carrying a certified PFAS claim — see certified vs "tested to". If PFAS is your priority, look for a certified PFOA/PFOS claim specifically, or a certified RO system.
This page is general information about certification standards, not a health or water-safety determination for your specific supply.
Frequently Asked Questions
NSF/ANSI 53. That's the health-effects standard covering lead, cadmium, mercury, chromium-6, and VOCs. NSF 42 covers taste and odor only, so a filter certified to 42 does nothing certified for lead. Always look for the number 53 (or 58 for an RO system) if lead is your concern.
Only if all you want is better taste and smell. NSF/ANSI 42 certifies aesthetic reduction — chlorine taste and odor, some particulates. It says nothing about lead, PFAS, or other health contaminants. Many inexpensive pitchers and filters are 42-only and are marketed in a way that implies more.
Emerging contaminants — a defined list of 15 including pharmaceuticals, over-the-counter drugs, and some pesticides and detergents, plus microplastics in newer scopes. It's an 'above and beyond' certification; a filter with 401 typically also carries 53.
NSF/ANSI 58 is the standard for reverse-osmosis systems (TDS reduction and a list of specific contaminants). NSF/ANSI 44 certifies salt-based water softeners for hardness reduction. NSF/ANSI 372 certifies that a product's materials are lead-free — a materials-safety cert, not a contaminant-reduction claim, so '372 certified' alone does not mean the filter reduces lead in your water.
No. NSF is one certifier, but WQA (Water Quality Association) and IAPMO R&D are equally valid accredited bodies that certify to the same NSF/ANSI standards. 'WQA certified to NSF/ANSI 53' is a genuine third-party certification. The real distinction isn't which logo it carries — it's whether it's certified by an accredited body at all, versus merely 'tested to' the standard.