NSF 401 vs 372: two things that are not alike
These two numbers get compared because they both appear on filter packaging as supporting credentials. They measure almost opposite things — and neither one is the health certification buyers usually assume they are.
The short answer
| NSF/ANSI 401 | NSF/ANSI/CAN 372 | |
|---|---|---|
| Type | Performance standard — what the product takes out | Material standard — what the product is made of |
| Measures | Reduction of up to 15 named trace compounds | Lead content, weighted average ≤ 0.25% of wetted surfaces |
| Covers | Pharmaceuticals, herbicides, flame retardants, BPA, DEET | Any component touching drinking water |
| Health-effects certification? | No | No |
| Covers PFAS? | No | No |
One is about removal. One is about content.
Standard 401 is a performance standard. It verifies that a system reduces specific emerging compounds — trace pharmaceuticals, hormones, herbicides, flame retardants — present at very low but measurable concentrations.
Standard 372 is a material standard. It verifies that the product itself contains almost no lead and therefore does not contribute lead to your water. It certifies nothing about what the product removes. As the Water Quality Association puts it, certification to 372 “is not a claim that the product completely removes any trace of lead from the water.”
A useful way to hold them apart: 401 is about the water leaving the filter. 372 is about the filter itself.
What they have in common
Just one thing, and it is the thing worth remembering: neither is a health-effects certification, and neither covers PFAS.
The health-effects standard is NSF/ANSI 53 (and 58 for reverse osmosis). If a product's certification list contains 401 and 372 but not 53 or 58, it has no verified claim against lead, arsenic, nitrate, cysts or PFAS — regardless of how impressive the list looks.
Why 372 in particular gets misread
Material-safety evaluation to Standard 372 is built into a genuine Standard 53 certification. That means a 372-only product can make a completely true statement that occupies the same visual and typographic space as a much stronger claim.
Add the fact that certification marks for components and end products can look identical, and that end-product certification does not extend to components (nor component certification to the end product), and you have a landscape where accurate statements routinely create inaccurate impressions.
Common questions
Is NSF 401 or NSF 372 better?
Neither — they measure different things. Standard 401 certifies reduction of trace emerging compounds; Standard 372 certifies that the product contains almost no lead. Neither is a health-effects certification.
Does NSF 372 mean a filter removes lead?
No. It means the product itself contains almost no lead and does not contribute lead to the water. Lead removal is certified under NSF/ANSI 53 or 58.
Do NSF 401 or 372 cover PFAS?
Neither covers PFAS. PFAS reduction claims are made under NSF/ANSI 53 and NSF/ANSI 58.
Reading a product page right now?
Skip the decoding. The selector only surfaces claims we have already verified against the certifier databases.
Get my recommendation