NSF Water Filter Certifications Decoded
What NSF 42, 53, 58, 401 and 473 mean on a filter box.
NSF/ANSI 42
Taste and odor — mainly chlorine. Nice to have, but not about health.
NSF/ANSI 53
Health contaminants like lead, cysts and some chemicals. The one to look for if you care about lead.
NSF/ANSI 58
Reverse osmosis systems. Covers TDS reduction and many health contaminants.
NSF/ANSI 401 and 473
401 covers emerging contaminants like medicines and pesticides. 473 covers PFOA and PFOS (PFAS).
Watch the wording
"Tested to NSF standards" is not the same as "NSF certified". Certified products are listed on NSF.org or WQA.org.
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