Tips for Taps Blog
Have you ever wondered what the ‘NSF’ acronym means on the packaging or websites of some water treatment products? Or, better yet, what it means when those three letters aren’t there? We’ll go over the basics in this blog post so you not only understand that designation, but are able to make more informed choices when you’re shopping around for water treatment products.
What is the NSF?
The National Sanitation Foundation (NSF) is an independent organization that develops standards and conducts product testing, inspection, and certification.
Note: This NSF is not to be confused with the National Science Foundation.
One of the many functions of the NSF is to develop standards for residential water treatment devices to ensure that the devices are composed of nontoxic materials and/or that they reliably and adequately remove certain contaminants. NSF works with the American National Standards Institute (ANSI) to develop these standards, referred to as NSF/ANSI standards. ANSI is a US-based non-profit organization that manages the development of voluntary consensus standards for products, services, techniques, systems, and personnel. 
Federal agencies that regulate drinking water (i.e. the EPA and FDA) do not regulate treatment devices, so certifications aim to provide unbiased information to help consumers decide which products will be effective for their water treatment needs. Some of the most popular NSF certifications address materials safety, structural integrity and specific contaminant reduction claims. 
What Organizations Can Certify Water Treatment Devices?
In addition to helping develop the standards for certification of drinking water treatment devices, NSF is also certified to conduct testing and certification of the devices to NSF/ANSI standards. This means that NSF both develops the standards and certifies devices when they meet said standards.
The Water Quality Association (WQA) is an organization that conducts research, education, and product testing and certification for the water treatment industry. The WQA tests drinking water treatment system components, water additives, pool and spa equipment, and food equipment that involves potable water. The agency provides the WQA Gold Seal Certification to products that have undergone testing in WQA's lab and meet certain quality standards, including NSF/ANSI standards. WQA tests and certifies products for safe materials, removal claims by manufacturers, and sustainability. WQA certifications are useful for consumers when considering which products will be effective for their needs. 
While the NSF and WQA are the most well known, there is yet another option for certification. The International Association of Plumbing & Mechanical Officials (IAPMO) has a research and testing arm, called IAPMO R&T, that certifies drinking water treatment devices. Similar to WQA, IAPMO R&T conducts testing in their labs, confers certification to NSF/ANSI standards, and has their own seal that indicates the devices were certified by an accredited organization. 
Certified products will bear the seal of the certifying body–finding the certification seal from NSF, WQA, or IAPMO R&T is a quick way to ensure that a drinking water treatment device is truly certified.
What Does ‘Certification’ Mean?
In the context of home water treatment products, ‘certification’ means that the product has performed to the standards that are stated in the specific certifications. Essentially, the product has passed the test that the agency designed. These tests are typically called ‘challenge tests’ and involve adding a specific amount of a contaminant to water and determining how much of that contaminant the product removes, then comparing that removal with the amount of removal specified in the standard. The standards also include verification of the safety of the materials used in the product, the structural stability of the product, the provision of proper information in the product literature and inspections of the manufacturing facilities. The certifications that we are focused on here are those that are developed jointly by the NSF and ANSI and are referred to as NSF/ANSI, followed by a number.
What Does ‘Tested To NSF Standards’ Mean?
Companies may state that their products have been ‘tested to NSF standards’, but this does not necessarily mean that they have been certified. It is harder to verify this claim for products that are not certified by one of the accredited certification bodies discussed above. Presumably, companies will make claims like this in order to provide evidence for the efficient reduction of certain contaminants without having to pay the certification fee. It is also possible that companies adhere to some of the requirements of the standard they claim but don’t follow all of the procedures required to get fully certified–claiming that the products are tested to NSF/ANSI standards is only partially true in this case. This type of claim may be perfectly valid, but it is important to make sure that the testing was done by a legitimate third-party laboratory and meets all of the requirements for certification–it is advisable to look for the testing results, if possible. A couple of key points to look out for in test results include testing the product beyond its listed capacity and achieving the contaminant reductions listed in the claims. And, of course, these claims are much more trustworthy if the products are certified.
Some Specific NSF/ANSI Certifications Explained
When it comes to NSF/ANSI certifications, there are a couple of points that apply to all certifications:
Each of these certifications is awarded on a contaminant by contaminant basis, meaning that a given product with a specific certification is not necessarily certified for the reduction of all contaminants that the certification standard covers. For example, the NSF/ANSI 42 standard covers many contaminants, including chlorine, chloramines and iron. A product may be NSF/ANSI 42 certified for chlorine only, which gives no information about the other contaminants covered by NSF/ANSI 42 certification.
The standards typically include requirements for the materials safety, design, and construction of the water treatment products. The distinct aspect of the standards is the contaminants that they are certified to remove.
Here is a quick run down of some of the most relevant certifications when it comes to home water treatment devices.
NSF/ANSI 42 Standard
The NSF/ANSI 42 standard is used to certify products for removing or reducing concentrations of contaminants that may cause negative aesthetic effects (i.e. color, taste and odor impacts). The standard establishes minimum requirements for removing or reducing the concentrations of compounds that cause an unpleasant taste, odor or color in drinking water, including aesthetic chlorine, chloramines, sizable particulates and microbes, manganese, iron, and zinc. NSF/ANSI 42 certification is used for both point of use (i.e. under the sink and pitcher filters) and point of entry systems. 
NSF/ANSI 53 Standard
The NSF/ANSI 53 standard is used to certify water treatment products for removing or reducing concentrations of contaminants that have the potential to cause health problems. The standard establishes minimum removal requirements for specific health-related contaminants. Some of the contaminants included in this certification are lead, asbestos, volatile organic compounds, Cryptosporidium, perfluoroalkyl substances (PFAS), and chromium. NSF/ANSI 53 certification is used for both point of use (i.e. under the sink and pitcher filters) and point of entry. 
NSF/ANSI 401 Standard
The NSF/ANSI 401 standard is used to certify water treatment products for removing or reducing concentrations of contaminants that have effects that are not fully researched (i.e., ‘contaminants of emerging concern’). The NSF established this certification due to increasing consumer concerns about potential effects from exposure to various emerging contaminants via drinking water. The standard establishes minimum requirements for the removal or reduction of certain emerging contaminants of concern, including a number of pharmaceuticals and pesticides. NSF/ANSI 401 certification is used for both point of use (i.e. under the sink and pitcher filters) and point of entry systems. 
NSF/ANSI 58 Standard
The NSF/ANSI 58 standard is used to certify point of use (e.g. under the sink) water treatment systems employing reverse osmosis, a high-pressure filter technology designed to remove a wide array of contaminants of concern. NSF/ANSI 58 establishes minimum requirements for total dissolved solids (TDS) reduction and contaminant removal or reduction. Some of the contaminants included in this certification are nitrate, lead, arsenic, volatile organic compounds, radium and fluoride. 
NSF/ANSI 44 Standard
The NSF/ANSI 44 standard is used to certify cation exchange water softeners for residential use. Water softening products covered by NSF/ANSI 44 reduce hardness by replacing calcium and magnesium with sodium or potassium. The standard establishes minimum requirements for the softening capacity and regenerated salt concentration of the products. It also dictates minimum removals for hardness minerals and certain other cations, including barium and radium. The NSF/ANSI 44 certification is used for both point of use (i.e. under the sink) and point of entry water softening systems. 
NSF/ANSI 55 Standard
The NSF/ANSI 55 standard is used to certify ultraviolet disinfection treatment systems designed to inactivate bacteria, protozoa, and viruses. The standard establishes requirements for the disinfection performance, material performance, and labeling information for certified products. There are two UV water treatment system classifications covered under this standard, Class A and Class B. Class A products have been tested and certified to reduce prevalent protozoa resistant to typical chlorine disinfection, including cryptosporidium and giardia, as well as bacteria and viruses to safe levels. Class B products have been tested and certified to further reduce microbe concentrations in water that is already deemed safe by health agencies. Class B certified products should not be used in the case of known harmful microbial contamination.
The NSF/ANSI 55 certification is used for both point of use (i.e. under the sink) and point of entry UV systems. Even Class A certified products are not recommended for cloudy, turbid water or water with a clear source of contamination. For example, these products should not be used to convert sewage wastewater to drinking water. 
NSF/ANSI 177 Standard
The NSF/ANSI 177 standard is used to certify point of use shower filters. Some studies suggest that elevated levels of chlorine in tap water left over from disinfection processes can dry out the skin and damage hair. NSF/ANSI 177 certified shower filters are certified for labeling information and the reduction of free available chlorine. 
NSF/ANSI 62 Standard
The NSF/ANSI 62 standard is used to certify distillation water treatment systems for residential use. Distillation systems heat water to its boiling point and collect the evaporated water, leaving behind most harmful contaminants. NSF/ANSI 62 establishes requirements for TDS reduction and the reduction of additional contaminants, including arsenic, chromium, mercury, nitrate, nitrite, bacteria, and protozoan cysts. The NSF/ANSI 62 certification is used for both point of use (i.e. under the sink) and point of entry distillation systems. 
Selected Reduction Claims
Location(s) of Products
Taste and Odor
Reduction of contaminants that may cause negative health impacts
Point of use
Point of entry
Reduction of contaminants that have effects that are not fully researched (i.e., ‘contaminants of emerging concern’)
Point of use
Point of entry
Reduction of TDS (required) and certain other contaminants by reverse osmosis systems
Point of use
Establishes requirements for the softening capacity and regenerated salt concentration, as well as the reduction of certain contaminants, for cation exchange water softeners
Certain other cations, including barium and radium
Point of use
Point of entry
Establishes requirements for the disinfection performance, material performance, and labeling information for ultraviolet disinfection (UV) treatment systems*
Prevalent protozoa resistant to typical chlorine disinfection, including Cryptosporidium and Giardia
Further reduction of microbes in water deemed safe by public health agencies
Point of use
Point of entry
Establishes requirements for labeling and contaminant reduction for shower filters
(Some studies suggest that chlorine can dry out the skin and damage hair)
Point of use
Reduction of TDS (required) and certain other contaminants by distillation units
Point of use
Point of entry
*UV products are not recommended for use with cloudy, turbid water or water with a clear source of contamination
Are Certified Water Treatment Products Better?
The short answer: not necessarily. Many uncertified products reduce contaminants to the same degree as their certified counterparts, it’s just hard to know if the manufacturer claims of contaminant reduction are accurate without certification by one of the accredited bodies discussed above. One reason that some companies don’t get their products certified is that the testing and certification can be expensive so they choose not to certify even if the products would pass the rigorous testing required to meet NSF/ANSI standards. On the other hand, the products may not be able to meet the standards so the companies don’t even try. In the end, certifications by accredited bodies give credence to manufacturer claims regarding contaminant reduction. Without certifications, you’ll need to look more deeply into the product and perhaps even test the treated water yourself.
If you have a treatment product and you’re concerned about its capabilities, or you just want to be sure that it’s reducing the contaminants you care about, consider purchasing one of our advanced tests (either city or well depending on your water source) to check the final water quality. Or buy two and do a before and after!
Ideal baseline for testing tap water provided by a local water utility–including metals, minerals, and chlorine-related byproducts.
Recommended test for those on a private well located near industrial, agricultural, or other human activity.
As always, if you have any water or testing-related questions, feel free to reach out to the SimpleLab team of water quality engineers, treatment experts, and chemists. They are always available to help you out. Send them a message any time at firstname.lastname@example.org.
Sources and References▾
- About NSF
- American National Standards Institute
- WQA Product Certification Program
- NSF/ANSI 42-2021: Drinking Water Treatment Units, Aesthetic Effects
- NSF/ANSI 42, 53 and 401: Filtration Systems Standards
- NSF/ANSI 53-2021: Drinking Water Treatment Units, Health Effects
- Emerging Contaminants | NSF
- NSF/ANSI 58: Reverse Osmosis Drinking Water Treatment Systems
- NSF/ANSI 44: Cation Exchange Water Softeners
- Ultraviolet (UV) Water Treatment Systems, NSF/ANSI 55-2021
- NSF/ANSI 55 Requirements for Ultraviolet Systems
- NSF/ANSI Drinking Water Treatment Standards
- NSF/ANSI 177-2019 - Shower Filtration Systems - Aesthetic Effects
- NSF/ANSI 62-2021 - Drinking Water Distillation Systems