NSF/ANSI 55: UV disinfection systems
Official title: Ultraviolet Microbiological Water Treatment Systems
Covers ultraviolet (UV) light systems. Class A systems inactivate or kill bacteria, viruses and cysts in contaminated water. Class B systems only reduce non-disease-causing bacteria in water that is already disinfected.
What it can cover
- Bacteria, viruses and cysts in contaminated water (listing claim: "Disinfection Performance, Class A")
- Non-disease-causing bacteria in disinfected water (listing claim: "Disinfection Performance, Class B")
What it does not
- Any chemical, such as lead, PFAS, nitrate or arsenic. NSF/ANSI 55 has no chemical reduction claims.
- Chlorine taste and odor
- Particles or cloudiness
The usual mistake
Treating any UV certification as disinfection. Only Class A is a disinfection claim. Class B units are meant for water that is already disinfected.
The fine print
- Check that the listing says Class A if the water may carry germs.
- NSF posted a 2026 edition of this standard.
Filters TapBuff has checked against a listing
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Sources
- NSF Standards for Water Treatment Systems, NSF. Checked Oct. 4, 2026.
- Search for NSF Certified Drinking Water Treatment Units (standards and reduction claims lists), NSF. Checked Oct. 4, 2026.
- Joint Committee on Drinking Water Treatment Units: recent documents (2026 editions of 44, 55, 62, 244, 401), NSF. Checked Oct. 4, 2026.
- Find WQA Certified Products (Gold Seal listings by standard and claim), Water Quality Association. Checked Oct. 4, 2026.