Certification standards
A certified system has been tested by an accredited body against a published standard, for the specific contaminants on its listing. Anything less is a marketing claim.
"Tested to NSF standards" is not certification. It means the maker paid a lab to run a test using the standard's method. Nobody checks the factory, repeats the test, or lists the product. Only a listing on the certifier's own website counts.
The standards
| Standard | What it covers | Applies to | What to check | Certifiers |
|---|---|---|---|---|
| NSF/ANSI 42 | Aesthetic (non-health) reduction claims: chlorine, chloramine, taste and odor, particulate (by size class), iron, manganese, zinc and total dissolved solids. Also tests material safety and structural integrity. | point-of-use and point-of-entry filters | The listing names each claim. A chlorine claim does not cover chloramine, which is a separate claim (a 3.0 mg/L challenge reduced to below 0.5 mg/L). Particulate claims name a class; Class I, the finest, means 85 percent reduction of particles 0.5 to 1 micron. | NSF, WQA, IAPMO, CSA, UL |
| NSF/ANSI 44 | Residential cation exchange water softeners regenerated with sodium or potassium chloride: hardness reduction, softening capacity, brine system accuracy, pressure drop, material safety and structural integrity. Optional claims for barium reduction, radium 226/228 reduction and salt and water efficiency. | whole-house (point-of-entry) salt-based water softeners | Rated capacity and service flow. Pressure drop at the rated service flow must not exceed 15 psi. An efficiency rating means at least 3,350 grains of hardness removed per pound of salt and is available only on demand-initiated (metered or sensor) softeners. Barium and radium are separate claims that must appear on the listing. | NSF, WQA, IAPMO, CSA, UL |
| NSF/ANSI 53 | Health effects reduction claims, more than 50 in all, including lead, cysts (Cryptosporidium, Giardia), VOCs, chromium, arsenic, PFOA/PFOS and a total PFAS claim. Also tests material safety and structural integrity. | point-of-use and point-of-entry filters | The listing names each contaminant; a system is only certified for the contaminants listed. PFOA/PFOS claims pass at 20 ppt combined, which is above EPA's 4 ppt limits. For lead, EPA's filter tool looks for reduction to 5 ppb under NSF/ANSI 53 together with NSF/ANSI 42 Class I particulate reduction. Whole-house listings also state a certified flow rate and capacity, which can be lower than advertised. | NSF, WQA, IAPMO, CSA, UL |
| NSF/ANSI 55 Class A | Ultraviolet systems designed to inactivate bacteria, viruses, Cryptosporidium and Giardia in contaminated but visually clear water. Minimum UV dose of 40 mJ/cm2. | point-of-entry and point-of-use UV disinfection systems | Class A units must include a UV sensor and alarm as a fail-safe. Confirm the listing says Class A (not Class B), note the certified flow rate, and meet the maker's pre-treatment limits for iron, manganese, hardness and turbidity. | NSF, WQA, IAPMO, CSA |
| NSF/ANSI 55 Class B | Ultraviolet systems for supplemental bactericidal treatment of disinfected public drinking water or other water already tested and deemed acceptable. Lower UV dose of 16 mJ/cm2, aimed at non-disease-causing bacteria. | point-of-entry and point-of-use UV systems on water that is already safe | Class B is not intended for contaminated water. Do not rely on it for a private well that has tested positive for coliform bacteria; look for Class A instead. | NSF, WQA, IAPMO, CSA |
| NSF/ANSI 58 | Reverse osmosis systems. Every certified system must reduce total dissolved solids by at least 75 percent. Optional claims include pentavalent arsenic, nitrate/nitrite, lead, chromium, fluoride, cysts, perchlorate and PFOA/PFOS. | point-of-use reverse osmosis systems | Each optional claim must appear on the listing. Arsenic claims cover pentavalent arsenic (arsenic V) only. A nitrate claim must be paired with a nitrite claim. The standard also defines an efficiency rating, the share of incoming water delivered as treated water; check it on the performance data sheet. | NSF, WQA, IAPMO, CSA, UL |
| NSF/ANSI/CAN 60 | Health effects of chemicals added directly to drinking water: disinfection and oxidation chemicals, pH adjustment, corrosion and scale control, softening, coagulation and other treatment chemicals. | chemicals fed by injection systems, such as chlorine, hydrogen peroxide and soda ash | It certifies the chemical product, not the pump or filter, and sets no performance requirements. Ask whether the chemical sold for your injection system is certified to it; most US and Canadian regulators require it for treatment chemicals. | NSF, WQA, UL |
| NSF/ANSI/CAN 61 | Health effects of materials that contact drinking water: limits on chemicals that leach from pipes, fittings, valves, tanks, filter housings, filter media and ion exchange resins. | components, process media and point-of-entry treatment equipment | It is a material safety standard only. NSF says it sets no performance, taste and odor or microbial growth requirements, so a 61 listing says nothing about what a filter removes. A '61 certified media' claim is not a certification of the finished system. | NSF, WQA, IAPMO, CSA, UL |
| NSF/ANSI 62 | Distillation systems, which heat water to boiling and collect the condensed vapor, leaving behind contaminants such as heavy metals. | point-of-use water distillers | NSF notes that some chemicals that turn readily into gas, such as VOCs, can carry over with the vapor. Check which contaminant claims are listed. | NSF, IAPMO |
| NSF/ANSI 177 | Shower filters, certified to reduce free available chlorine only. | shower filters installed just before the showerhead | The claim covers free chlorine only. NSF notes certified shower filters have not been evaluated in the presence of chloramine, so the certification does not apply if your utility uses chloramine. | NSF, IAPMO |
| NSF/ANSI 244 | Supplemental microbiological filters that protect against intermittent bacteria, virus and cyst contamination of otherwise safe drinking water. Also covers material safety and structural integrity. | filters on treated public water supplies or water determined to be microbiologically safe | It is not for untreated or contaminated water, such as a private well with coliform bacteria. For water of unknown microbiological quality, look for NSF P231 or a Class A UV system. | NSF, IAPMO |
| NSF/ANSI 330 | Glossary of drinking water treatment unit terminology: definitions of terms for materials, design, construction and performance testing used across the NSF treatment standards. | the NSF/ANSI treatment standards themselves; it contains no product requirements | Nothing to check on a product. A glossary has no pass or fail tests, so a product claiming certification to NSF/ANSI 330 is not describing a performance certification. | |
| NSF/ANSI/CAN 372 | Lead content of drinking water system components. It verifies the Safe Drinking Water Act lead-free definition: a weighted average of no more than 0.25 percent lead across wetted surfaces, and 0.2 percent for solder and flux. | pipes, fittings, faucets, valves and water treatment products | It certifies the lead content of the product's own materials, not whether the product removes lead from water. For lead removal, look for NSF/ANSI 53 or 58 with a lead claim. | NSF, WQA, IAPMO, CSA |
| NSF/ANSI 401 | Emerging compounds and incidental contaminants: up to 15 named compounds detected at trace levels in drinking water, including some prescription and over-the-counter drugs, herbicides, pesticides and BPA. | point-of-use and point-of-entry filters | Each compound is a separate claim, so check which are listed. A 401 listing does not cover PFAS, lead or chlorine; those claims sit under NSF/ANSI 53, 58 or 42. | NSF, WQA, IAPMO |
| NSF P231 | Microbiological water purifiers, based on EPA's 1987 Guide Standard and Protocol for Testing Microbiological Water Purifiers: 6-log (99.9999 percent) bacteria, 4-log (99.99 percent) virus and 3-log (99.9 percent) cyst reduction. | point-of-use purifiers intended for water of unknown microbiological quality | It is a protocol, not an American National Standard. Confirm the listing names P231 and the specific purifier model, and follow the replacement schedule, since purification claims depend on it. | NSF, IAPMO, UL |
| NSF P473 | PFOA and PFOS reduction protocol from 2016: a challenge of 1,000 ppt PFOS plus 500 ppt PFOA reduced to 70 ppt combined. | point-of-use and point-of-entry filters | PFOA and PFOS claims were folded into NSF/ANSI 53 and 58 in 2019, with a tighter 20 ppt combined pass level. A P473 listing today is an older-style claim covering PFOA and PFOS only, and its pass level is far above EPA's 4 ppt limits. | NSF, IAPMO |
| CSA B483.1 | Canadian national standard for drinking water treatment systems: plumbing, mechanical and electrical requirements for plumbed-in point-of-use and point-of-entry systems and non-plumbed point-of-use systems. The 2021 edition added point-of-entry, lead content and inline valve requirements. | point-of-use and point-of-entry treatment systems sold in Canada, often listed alongside NSF/ANSI standards in the US | It is not a contaminant reduction claim. Pair it with NSF/ANSI 42, 53, 55 or 58 listings to know what the system actually removes. | CSA, IAPMO, WQA |
| IAPMO/ANSI Z601 | Scale reduction devices for residential water heating, published 2018: the device must reduce scale by at least 70 percent against untreated controls. | salt-free conditioners (template-assisted crystallization and similar) and other scale reduction devices | It measures scale, not hardness; a passing device does not soften water. The Water Quality Association argued for the 80 percent pass mark used in Germany's DVGW W 512. | IAPMO |
| DVGW W 512 | German test for scale control devices: hard water runs through the device into a small water heater at an accelerated 80 °C for about three weeks beside untreated controls, and the device must cut scale formation by 80 percent. | salt-free conditioners and other physical scale control devices | A DVGW certificate applies to a specific device. Published test results for a technology such as TAC are not a certificate for the product you buy. | DVGW |
| EPA WaterSense (point-of-use RO) | Water efficiency label for point-of-use reverse osmosis systems, specification released November 2024: 2.3 gallons or less sent to the drain per gallon of treated water (typical systems send five or more), a membrane that lasts at least one year, baseline TDS reduction, and certification of any additional contaminant claims. | point-of-use reverse osmosis systems | The label covers efficiency and membrane life. Contaminant claims still need an NSF/ANSI 58 or 53 listing that names each contaminant. | EPA-licensed certification bodies |
| WQA Gold Seal | The Water Quality Association's certification mark for products tested and certified to NSF/ANSI, NSF/ANSI/CAN and other standards, with annual facility audits and periodic retesting. WQA is one of five equally accredited certifiers for drinking water treatment products. | treatment units, system components, treatment chemicals and water softeners | The seal alone does not say which standard or contaminant is covered. Look up the exact model in WQA's product finder and read the listed standards and claims. | WQA |
| Tested to (not certified) | Marketing language meaning the maker, or a lab it paid, ran tests based on a standard's protocol. It is not a certification. | any product that uses phrases such as 'tested to NSF/ANSI 53', 'meets NSF standards' or 'SGS tested' | A certified product appears in the public listings of an accredited certifier (NSF, IAPMO, WQA, CSA or UL) and is subject to annual factory audits and retesting. 'Tested to' has none of that. WQA and IAPMO both stress the difference between a standard and a certification. Also watch for 'uses NSF-certified media' or '61 certified components', which describe parts, not the system's performance. |
How to check a listing yourself
- Find the certifier named on the box or product page: NSF, IAPMO, WQA or CSA.
- Search that certifier's own listings site for the brand: NSF, IAPMO, WQA.
- Match the exact model number. Replacement cartridges and whole systems are listed separately.
- Read the contaminant list on the listing. A system certified to NSF/ANSI 53 for lead is not certified for PFAS unless PFOA and PFOS appear on its listing.
Systems in our database with a system-level certification
| System | Certified to |
|---|---|
| SpringWell LCR-1 | NSF/ANSI 53 |
| US Water Systems Pioneer (Enpress CTA0840BBBKP5-04C00) | NSF/ANSI 53 (lead, cyst, PFOA/PFOS), NSF P473 (PFOA, PFOS), CSA B483.1 |
| Aquasana HealthShield WH-HS | NSF/ANSI 53, NSF/ANSI 401, CSA B483.1 |
| AquaTru Classic (AT2000 series) | NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 58, NSF/ANSI 401, NSF/ANSI 372 |
| Waterdrop G3P800 (WD-G3P800-W) | NSF/ANSI 58, NSF/ANSI 53, NSF/ANSI 42, NSF/ANSI 372 |
| Waterdrop X16 (WD-X16) | NSF/ANSI 58, NSF/ANSI 42, NSF/ANSI 372 |
| Aqua-Pure (formerly 3M Aqua-Pure, Solventum) AP904 | NSF/ANSI 42 |
| Rheem Preferred RHS32 | NSF/ANSI 44, NSF/ANSI 372, CSA B483.1 |
| VIQUA VH410 | NSF/ANSI 55 Class B, listed model VH410-V only (with flow restrictor, 14 gpm); the plain VH410 priced here is not the listed model, CSA B483.1, listed model VH410-V only |
| VIQUA Arros 15 | NSF/ANSI 55 Class B, listed model Arros 15-V only (with flow restrictor, 9.4 gpm at 16 mJ/cm2 and 70% UVT); the plain Arros 15 priced here is not the listed model, CSA B483.1, listed model Arros 15-V only |
| LUMINOR BLACKCOMB 5.1 LB5-101B | NSF/ANSI 55 Class B (listed as LB5-10XB, X = plug type, 13 gpm), CSA B483.1 |
| Watts OneFlow+ OFPSYS | NSF/ANSI 372 (lead-free materials only) |
| iSpring RCC7AK | NSF/ANSI 58 |
| APEC ROES-50 | NSF/ANSI 58, NSF/ANSI 372 |
| Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2) | NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 58, NSF/ANSI 401, CSA B483.1, NSF/ANSI 372 |
| AquaTru Carafe (AT100 series) | NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 58, NSF/ANSI 401, NSF/ANSI 372 |
| AquaTru Freestanding Model 1 (ATFS-1-W) | NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 58, NSF/ANSI 401 |
| Pentair FloPlus Protect 20BB (150736) | NSF/ANSI 53 |
| Pentair FreshPoint GRO-575B (161112) | NSF/ANSI 58, NSF/ANSI 53, NSF/ANSI 42, NSF/ANSI 401, CSA B483.1, NSF/ANSI 53, NSF/ANSI 372 |
37 of 56 systems in the database hold no system-level certification. Show only certified systems.