The short version: NSF/ANSI P473 is the only widely recognized certification that specifically tests a drinking water filter for PFOA and PFOS reduction. If a filter does not hold P473 — or publish equivalent independent third-party testing against the same protocol — its PFAS claims are not verified.
This matters because most pitcher filters do not hold it. The Brita on your counter, the cheap pitchers at the grocery store, the activated-carbon faucet attachments — almost none are P473 certified. They are tested for chlorine taste-and-odor reduction (NSF/ANSI 42) and many are tested for some health-effects contaminants like lead (NSF/ANSI 53), but PFAS is a separate test.
What NSF International is
NSF International is an independent, accredited, third-party public-health organization. They do not sell water filters. They write the standards that water filters are tested against, and they run the test labs that issue certifications. When a filter "holds NSF/ANSI 42" or "holds NSF/ANSI P473," it means NSF or another accredited lab tested an actual production-line unit, broke it open, ran water through it, and measured the contaminant reduction at the outlet against the standard.
NSF certifications are public. You can search the NSF certified products database by brand name and find the exact products certified to each standard. That public-record verifiability is what separates a real certification from a marketing claim.
What NSF/ANSI P473 specifically tests
P473 was published as a protocol amendment to address PFOA and PFOS. The NSF guide explains the headline:
- The filter must reduce PFOA from a 1.5 parts-per-billion influent to below 0.07 parts per billion (70 parts per trillion) at the outlet
- Same threshold applies to PFOS
- Reduction has to be maintained for the rated cartridge life — not just the first gallon
That 70 parts-per-trillion threshold was set when EPA's prior health advisory was 70 ppt. It is now a much weaker threshold than the April 2024 EPA rule, which set the legally enforceable Maximum Contaminant Level for PFOA and PFOS at 4 parts per trillion. So a filter that holds P473 today is meeting a standard that is 17x weaker than the federal regulation that utilities have to comply with by 2029.
That is not as bad as it sounds. The P473 protocol (the testing method) is sound — the threshold is what is dated. Most certified P473 filters in independent test reports show reduction levels well below the 70 ppt requirement, often into single-digit ppt. The point is: do not assume "P473 certified" means "removes all PFAS to safe levels." Read the actual independent test report when the brand publishes one.
P473 vs NSF/ANSI 401 — different standards
This is a common point of confusion: NSF/ANSI 401 is the emerging contaminants standard. It tests for 15 different compounds — pharmaceuticals, pesticide metabolites, BPA, etc. PFOA and PFOS were originally covered under 401 in some product certifications, then split out into the dedicated P473 protocol.
A modern filter might hold one, the other, or both. They are separate certifications and you cannot infer one from the other.
For PFAS specifically, P473 is the certification that tells you what you want to know.
How to verify a brand's P473 claim
The verification process takes 60 seconds:
- Go to nsf.org/certified-products-systems (the NSF Listing search)
- Type the brand name (e.g., "Clearly Filtered" or "AquaTru")
- Filter by Standard 53 / P473 (or just search the product line)
- Confirm the specific product appears in the listing
If a brand prominently advertises "NSF certified for PFAS removal" but the product does not appear in the NSF database, that is a marketing claim, not a certification. The filter may still be effective — many brands publish their own independent third-party lab reports — but the words "NSF certified" should appear in the NSF database for that exact product to mean what they sound like.
Clearly Filtered, AquaTru, and Epic Pure all publish independent test data against NSF protocols including P473. Some hold the formal NSF certification; others publish reports from accredited third-party labs testing to the same protocol. We cite the lab report URL on each individual product page.
Why most pitchers do not hold P473
Three reasons:
- It is expensive. NSF certification is a real lab test, repeated annually, with audit fees in the thousands of dollars.
- Activated carbon does not target PFAS well. The standard pitcher cartridge is granular activated carbon (GAC). GAC reduces chlorine, taste, and some VOCs effectively. It does not capture the long-chain PFAS molecules well enough to meet P473 without additional media (like ion-exchange resin).
- The standard requires sustained performance. A filter has to keep meeting the threshold across its rated cartridge life. Cheaper carbon cartridges lose performance fast.
The combination is why the certified P473 list is short. It is not random — the filters on it are built differently than a standard Brita.
What this means in practice
If PFAS is your concern, the certification you ask about is NSF/ANSI P473, not "NSF certified" generically. If the brand cannot point to the listing, ask for the independent third-party test report instead. If they cannot point to either, assume the PFAS claim is unverified.
For our specific picks across pitcher, countertop, and gravity systems, see Best PFAS Water Filters.
Frequently asked questions
(See structured FAQ at the bottom of this page for full answers.)
