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By Clean Water Adviser Editorial Team - Updated October 4, 2026 - 6 min read

NSF 42 vs 53 vs 58 - Water Filter Certifications Explained

Not all NSF certifications are equal. Here's what each one actually means - and why it matters when buying a water filter.

Key takeaway

NSF/ANSI 42 is about taste, smell and appearance. For PFAS or lead, NSF itself points to standards 53 and 58. The number alone does not settle it: every product is certified for its own list of contaminants, so the listing matters more than the badge.

Quick comparison

StandardNSF calls itClaims NSF namesApplies to
NSF/ANSI 42Aesthetic effectsChlorine, taste and odor, chloramine, particulate, iron, manganese, zinc, TDSPoint-of-use and whole house
NSF/ANSI 53Health effectsOver 50 possible claims, among them lead, Cryptosporidium, VOCs, chromium. PFAS claims sit here tooPoint-of-use and whole house
NSF/ANSI 58Reverse osmosis systemsTDS reduction is required. Optional: fluoride, arsenic, lead, nitrate, chromium, VOCs and others. PFAS claims sit here tooPoint-of-use RO only
NSF/ANSI 401Emerging compoundsUp to 15 named compounds: prescription and over-the-counter drugs, herbicides, pesticidesPoint-of-use and whole house

Source: NSF, standards 42, 53 and 401, standard 58 and PFAS in drinking water. Read 1 October 2026.

NSF adds one line that changes how to read every badge: the numbers show the order in which the standards were written. They are not a ranking, and 58 is not "better than" 53.

NSF/ANSI 42 - what it means

NSF's own name for standard 42 is "Aesthetic Effects". It sets minimum requirements for systems that reduce contaminants with no health effect. The claims NSF lists under it are chlorine, taste and odor, chloramine, particulate, iron, manganese, zinc and total dissolved solids.

Two things follow. A filter with only a 42 certificate has been checked for how the water tastes and looks, and nothing on NSF's list for this standard is a health claim. And "certified to NSF 42" still does not tell you which of those eight items the product was tested for: claims vary by product.

The same certificate does cover more than performance. NSF tests material safety and structural integrity under 42 as well.

In our catalogue, confirmed for 42: AquaTru Classic, AquaTru Carafe, Aquasana Claryum 3-Stage Max Flow, Aquasana Clean Water Machine, Waterdrop G3P600, Clearly Filtered Water Filter Pitcher, Waterdrop Lucid Pitcher PT-07, Waterdrop G3P800, Waterdrop X Series X8-A (Alkaline), Brita UltraMax Large Dispenser, Aquasana SmartFlow Reverse Osmosis.

Maker lists 42, we could not confirm it: Aquasana Rhino EQ-1000, Clearly Filtered 3-Stage Under-Sink System, SpringWell CF+.

NSF/ANSI 53 - what it means

Standard 53 is "Health Effects". NSF describes it as certification to reduce a contaminant with a health effect, with those effects defined by the EPA and Health Canada. It offers more than 50 separate reduction claims. The ones NSF names as most common are lead, Cryptosporidium, VOCs and chromium.

That number is the reason a bare "NSF 53" on a box says very little. One filter can hold 53 for lead alone. Another can hold it for lead, cysts and a list of VOCs. Both print the same badge.

PFAS belongs here as well. NSF names standards 53 and 58 as the ones under which a PFAS reduction claim is certified, and says a filter has to bring PFAS below 20 parts per trillion to make that claim.

Standards 42 and 53 both cover adsorption and filtration. Carbon filters are the example NSF gives.

In our catalogue, confirmed for 53: AquaTru Classic, AquaTru Carafe, Aquasana Claryum 3-Stage Max Flow, Aquasana Clean Water Machine, Waterdrop G3P600, Waterdrop Lucid Pitcher PT-07, Waterdrop G3P800, Brita UltraMax Large Dispenser, Aquasana SmartFlow Reverse Osmosis.

Maker lists 53, we could not confirm it: Aquasana Rhino EQ-1000, Clearly Filtered Water Filter Pitcher, Clearly Filtered 3-Stage Under-Sink System, SpringWell CF+.

NSF/ANSI 58 - what it means

Standard 58 is written for point-of-use reverse osmosis systems. Only one performance claim is required under it: reduction of total dissolved solids. Everything else is optional, and the maker decides which of those claims to certify.

The optional list on NSF's page is long: fluoride, arsenic, lead, nitrate and nitrite, hexavalent and trivalent chromium, cadmium, barium, copper, selenium, radium 226/228, perchlorate, VOCs, cysts, turbidity and asbestos. So an RO system certified to 58 has not automatically been tested for fluoride or arsenic. It may have been tested for TDS and nothing more.

Besides contaminant reduction, 58 covers material safety, structural integrity, and the system's efficiency and recovery ratings.

In our catalogue, confirmed for 58: Waterdrop M6SL, Waterdrop M6H, AquaTru Classic, AquaTru Carafe, Bluevua RO100ROPOT-Lite, APEC ROES-50, Waterdrop G3P600, Waterdrop G3P800, iSpring RO500, Waterdrop X Series X8-A (Alkaline), Aquasana SmartFlow Reverse Osmosis.

Maker lists 58, we could not confirm it: Waterdrop D6.

The APEC ROES-50 is a good example. WQA lists it under NSF/ANSI 58 with one reduction claim: TDS. Other APEC models in the same listing carry fluoride, arsenic and lead claims; the ROES-50 does not. Certified claims are specific, and they change, so check the exact contaminant you care about in the listing rather than trusting a headline number on a box.

NSF/ANSI 401 - what it means

Standard 401 covers what NSF calls emerging compounds or incidental contaminants: up to 15 individual substances that published studies have found in drinking water at trace levels. NSF groups them as prescription drugs, over-the-counter medications, herbicides, pesticides and chemical compounds, and notes that they are not yet regulated by the EPA or Health Canada.

NSF frames these as substances that can affect how people perceive their water quality. A 401 certificate, like the others, lists specific compounds per product, up to those 15.

In our catalogue, confirmed for 401: AquaTru Classic, AquaTru Carafe, Aquasana Claryum 3-Stage Max Flow, Aquasana Clean Water Machine, Aquasana SmartFlow Reverse Osmosis.

Two systems we cover in detail
SpringWell CF+
Whole house - maker lists NSF 53, not confirmed by us
No purchase link for this one yet
APEC ROES-50
Under-sink RO - WQA lists it under NSF/ANSI 58 for TDS reduction
Check price on Amazon ↗

What the filters in this catalogue actually carry

A certification on a box is a claim until somebody checks the listing. We split our catalogue in two: what we found in a certifier's own public listing (NSF, IAPMO R&T or WQA), and what we could not find there. The second group is not a blacklist. It means the paperwork is not where we could read it, so judge those filters on the specifications instead.

Confirmed

Listed by the maker, not confirmed by us

How to verify NSF certification

Don't trust marketing claims. NSF keeps a public search of certified drinking water treatment units. Type at least three letters of the maker or the model, pick the standard from the list (42, 53, 58, 401 and the rest are separate entries), and open the listing. It shows the exact claims that model holds, contaminant by contaminant.

NSF is not the only body that certifies to these standards. IAPMO R&T and the Water Quality Association are accredited to certify to the same NSF/ANSI standards, and many brands use them instead: the Waterdrop models we cover are listed with IAPMO, and the Aquasana, APEC and Brita models with WQA. If a model is missing from the NSF search, look in the IAPMO R&T directory and the WQA product search before you conclude it is not certified.

NSF closes its own overview with the same warning: certification to a standard does not mean a filter reduces every possible contaminant, so check the one you care about.

The lists on this page come straight from our product data. A model moves to "confirmed" only after we have read its listing ourselves. Until then it stays marked as the maker's claim, however well known the brand.

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