NSF certification is a mark of quality and safety for products, ensuring they meet strict standards set by the National Sanitation Foundation. This independent organization tests and certifies products, ensuring they comply with public health and safety standards.
What is an NSF Certified UV Water System?
What are NSF Standards for Water Filters?
NSF standards ensure quality and safety of products-- which is especially important when it comes to water filters and UV water disinfection systems. In fact, you can figure out specifically what a water filter does or removes by looking at the NSF label.
NSF International works to protect consumers by providing third-party testing, written standards, and validation of products available to the public.
- Third-Party Testing: NSF conducts rigorous testing to ensure products are safe and effective.
- Quality Assurance: Products with NSF certification have been tested for quality and safety.
- Consumer Trust: NSF-certified products are trusted by consumers for their reliability and safety.
NSF Certifications for Water Treatment
Although this page is devoted to explaining NSF certification for UV water disinfection, it's important to understand that there are a number of certifications available to ensure the safety and quality performance of many water treatment options. Here are a few examples:
NSF/ANSI 42
Water filters, such as under sink reverse osmosis filters, are certified to reduce impurities that affect taste and odor.
NSF/ANSI 58
This certification is the standard for point-of-use reverse osmosis systems.
NSF/ANSI 55
This certification applies to ultraviolet water treatment systems. Class A UV sterilizers use ultraviolet light to inactivate or kill waterborne bacteria, cysts and viruses. Class B systems are certified to reduce the amount of non-disease-causing bacteria in drinking water.
Importance of NSF Certification
NSF standards are widely accepted by government regulatory bodies. When a water filtration product has been NSF certified, this means it has passed through rigorous testing and met the standardized requirements.
- Compliance with Regulations: Recognized by local, state, federal, and international regulatory bodies.
- Continuous Monitoring: Regular re-testing and unannounced inspections to maintain certification.
- Product Integrity: Ensures products meet ongoing quality and safety standards.
You can look up specific water filtration products in the NSF database to see what contaminants the system is certified to protect against.
NSF.org "What You Need to Know About Finding the Best Water Filter for Your Home"
What NSF Certifications Are Important in UV Water Disinfection?
For UV water treatment, the NSF has established two certification classifications: NSF/ANSI 55 "Class A" and "Class B". These certifications validate a manufacturer's product claims.
When a UV system becomes NSF/ANSI 55 certified, it means the UV system complies with the strict standards and procedures imposed by NSF, including extensive product testing and material analyses.
UV system manufacturers (such as VIQUA), are subjected to unannounced plant inspections and regular re-testing of products to maintain the NSF certification. It is not a one-time event but an ongoing review process. NSF certification is recognized by regulators at all levels from local and state, to federal and international.
What is NSF/ANSI 55 Class A Certification?
Class A systems (40 mJ/cm2) are designed to inactivate common waterborne pathogens* including cryptosporidium, giardia, E. coli, legionella, norovirus, and hepatitis A virus. † remove microorganisms, including bacteria, viruses, Cryptosporidium oocysts and Giardia cysts from contaminated water to a safe level. These systems are not intended for the treatment of water that has an obvious contamination or intentional source, such as raw sewage. Class A systems are not intended to convert wastewater to drinking water. The systems are intended to be installed on visually clear water (not colored, cloudy or turbid).
While both certification for Class A and B require rigorous testing, Class A systems include UV dosage and fail-safe requirements that go above and beyond those of Class B systems.
Best Selling NSF/ANSI 55 Class A UV Systems
Certified to NSF/ANSI Standard 55 Class A, the Pro10 is a Point of Entry (POE) ultraviolet system designed to treat up to 10 gpm@40mJ/cm² and features an amalgam lamp that provides higher strength as well as up to 2 years of lamp life.
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The VIQUA Pro20 Monitored UV system is NSF Class A certified to treat flow rates of up to 20 GPM and is perfect for large homes (4-7 Bedrooms) and commercial use. The Pro20 ultraviolet water treatment system features an amalgam lamp that provides higher strength and up to 2 years of lamp life.
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What is NSF/ANSI 55 Class B Certification?
Class B Systems (16 mJ/cm2) are designed for "supplemental" bactericidal treatment of public or other drinking water that has been deemed acceptable for human consumption.
Basically, Class B systems may claim to reduce non-disease-causing bacteria an nonpathogenic nuisance microorganisms in drinking water, but cannot claim to disinfect microbiologically unsafe water.
Key Takeaways:
What are the Similarities and Differences Between NSF Class A & Class B Certified UV Systems?
- Both Class A and Class B systems share strict requirements for safety of materials in contact with drinking water and for structural integrity of systems connected to a pressurized water supply.
- Both Class A & B must include flow restrictors to assure that the UV dosage cannot drop below that which results from testing. However, Class A systems require a higher UV dosage.
- NSF/ANSI 55 requirements specify that Class A ultraviolet systems incorporate an alarm or fail-safe element into their design. Thus, all Class A systems include sensors that provide an audible and visual indication that the system is not performing to standard.
- During the Class A certification process, system alarms must perform properly even during low-dosage conditions.
- Although Class B systems are not required to have a UV sensor, if a class B system is equipped with a sensor, then it must meet the necessary requirements.
For a complete list of NSF water treatment standards, visit NSF.org. If you have any questions about NSF testing/certifications, please call our customer support team at 469-521-9920.
NSF Certified UV Water Purifiers Frequently Asked Questions
What does NSF certification mean for a water filter or UV purifier?
NSF (National Sanitation Foundation) certification means a water treatment product has been independently tested and confirmed to meet strict public health and safety standards — providing third-party assurance that it actually performs as claimed. For UV systems, it verifies the system delivers a proven germicidal UV dose under real operating conditions. NSF certification is recognized by regulators at local, state, federal, and international levels, and manufacturers must pass unannounced inspections and periodic retesting to maintain it. Browse our NSF-certified UV systems.
What is the difference between NSF Class A and Class B UV systems?
Both fall under NSF/ANSI Standard 55 but serve different purposes. Class A systems deliver a UV dose of 40 mJ/cm² and are certified to disinfect microbiologically unsafe water — killing bacteria, viruses, Cryptosporidium, and Giardia. They are the right choice for private wells and any water source that cannot be guaranteed biologically safe. Class B systems deliver 16 mJ/cm² and are certified only for supplemental treatment of water already confirmed safe for drinking — they cannot be used as a primary disinfection step. Browse Class A certified UV systems or the full range of whole-house UV systems.
Do I need an NSF certified UV system for my home?
NSF certification is not legally required for residential use in most areas, but it is the strongest available proof that a system delivers the UV dose it claims. For city water households using UV as a supplemental measure, a non-certified system may be sufficient. For homes on private wells or any source with confirmed or suspected biological contamination, an NSF/ANSI 55 Class A certified system is strongly recommended — it guarantees the ability to treat microbiologically unsafe water to a safe level. See our guide to best UV systems for well water.
What does NSF/ANSI 55 certification specifically cover?
NSF/ANSI Standard 55 is the certification standard for ultraviolet water treatment systems. It verifies the system delivers a sufficient germicidal UV dose to inactivate bacteria, viruses, Cryptosporidium oocysts, and Giardia cysts. It also certifies that all materials contacting drinking water are safe and that the system maintains structural integrity under pressurized supply. Class A systems carry additional fail-safe requirements — including flow restrictors to ensure the UV dose never drops below the certified minimum — that Class B systems are not subject to. Learn more about removing bacteria from drinking water and removing viruses from drinking water.
Is NSF Class A certification required for treating well water?
Not legally required in most US states, but strongly recommended. Private wells are not regulated under the Safe Drinking Water Act, meaning biological contamination can go undetected. A Class A system guarantees disinfection at 40 mJ/cm² — sufficient to inactivate bacteria, viruses, Giardia, and Cryptosporidium in water that cannot be pre-certified as safe. Well water should be tested before selecting a system — elevated iron, hardness, or turbidity may require sediment pre-filtration for the UV system to work effectively. Browse our best UV systems for well water.
How do I know if my UV water purifier is NSF certified?
Look for the NSF mark on the system or its product documentation, along with the specific standard — for example, NSF/ANSI 55 Class A. You can also verify certification directly at NSF.org using the product database. When shopping with ESP Water, our NSF-certified UV systems are clearly labeled in the product listings. For maintenance that keeps your certified system performing as designed, see how to replace a UV lamp and shop genuine replacement UV lamps and sleeves.
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