Glossary · Certification and standards

What Is NSF/ANSI 53? The Standard for Health Claims

NSF/ANSI 53Drinking Water Treatment Units: Health Effects

The NSF/ANSI standard that certifies a filter reduces specific contaminants with health effects, such as lead, cysts, VOCs or PFOA and PFOS, claim by claim.

  • NSF/ANSI 42Aesthetic effects: taste, odor, particlesChlorine, chloramine, taste and odor, particulates, zincPitchers, faucet, under-sink, fridge and whole-house filters
  • NSF/ANSI 53Contaminants with health effectsLead, cysts, VOCs, mercury, PFOA/PFOSPitchers, faucet, countertop, under-sink and fridge filters
  • NSF/ANSI 58Reverse osmosis drinking water systemsTDS (required); optional claims such as lead, fluoride, arsenic, nitrateReverse osmosis systems, mostly under-sink
  • NSF/ANSI 401Emerging compounds and incidental contaminantsIbuprofen, BPA, DEET, some herbicides, microplasticsPitchers, faucet, under-sink and fridge filters
  • NSF/ANSI 44Cation exchange (salt-based) water softenersHardness, salt efficiency, barium, radium 226/228Whole-house water softeners
  • NSF/ANSI 55Ultraviolet (UV) systems for microbesClass A: bacteria, viruses, cysts; Class B: nuisance microbesWhole-house and point-of-use UV systems
  • NSF/ANSI 177Shower filters, aesthetic effects onlyFree available chlorineShower filters
NSF/ANSI 53 among the drinking water standards: it is the one for health contaminants.

At a glance

Official name
Drinking Water Treatment Units, Health Effects
Common claims
Cysts, lead, VOCs, mercury, PFOA, PFOS, Total PFAS
Products
Pitchers, faucet, countertop, under-sink and fridge filters
Lead test
Water with 150 ppb lead, run past the filter's rated life
Certified by
NSF, WQA, IAPMO R&T, CSA Group and UL

If you want a filter for a health reason, such as lead from old pipes or PFAS in your utility’s water, NSF/ANSI 53 is usually the standard to look for. But the number on the box is only half the answer: what matters is which contaminants the model is certified for.

What does NSF/ANSI 53 cover?

NSF calls 53 the nationally recognized standard for certifying drinking water treatment systems to reduce contaminants, in its guide to lead filters. On NSF’s listings for the standard, the most common claims are cyst reduction and lead reduction. Others include VOCs and individual chemicals such as benzene, pesticides such as atrazine, mercury, asbestos, PFOA, PFOS and “Total PFAS”.

Each claim is certified separately. A pitcher can be certified to NSF/ANSI 53 for lead and nothing else. That’s why the EPA’s consumer tool for lead filters asks you to look for both the standard and a lead reduction claim.

For lead, NSF says certified filters are tested with water containing 150 parts per billion of lead, for longer than the filter’s claimed service life. Certification also requires the maker to state the filter’s capacity, the volume of water it can treat before the cartridge must be replaced.

Does NSF/ANSI 53 mean a filter removes PFAS?

Only if PFAS is on the listing. The EPA tells you to look for certification to NSF/ANSI 53, or 58 for reverse osmosis, for PFAS reduction, and notes that as of April 2024 these certifications focused on PFOA and PFOS. It also says the current standards don’t yet show that a filter brings PFAS down to the levels in its drinking water rule. Our guide to filters that remove PFAS checks the listings model by model.

How do you check a 53 certification?

Find the exact model and replacement cartridge in the certifier’s own listing (NSF, WQA, IAPMO R&T, CSA Group or UL) and confirm your contaminant is listed. Replace the cartridge at its rated capacity, or it stops doing what the listing says.

Not sure you need one? Check your water quality report or test your well first. For lead, our guide to lead in drinking water explains how to find out if you have a lead service line and how to test.

Published by the Checked Water editorial team

Sources

  1. NSF Listings: NSF/ANSI 53 Drinking Water Treatment Units, Health Effects (Source, NSF, 2026)
  2. Certified Product Listings for Lead Reduction (Source, NSF, 2026)
  3. Consumer Tool for Identifying Point-of-Use and Pitcher Filters Certified to Reduce Lead in Drinking Water (Clinical guideline, US EPA, 2024)
  4. Reducing PFAS in Your Drinking Water with a Home Filter (Clinical guideline, US EPA, 2026)

Where NSF/ANSI 53 comes up