Get the Facts: Understanding NSF Certification for Water Filters

Photo of author

By Eric Phillips


From lead to pesticides to the taste of chlorine, there are plenty of contaminants in our water and we want them gone.

With a wide range of water filters available, it can be challenging to determine which ones are effective. Many contaminants are undetectable by taste or odor. Reliance on a water filter requires trust.

That's why NSF certification is crucial to understand. The National Sanitation Foundation has established safety standards in public health and the environment for over 75 years. While there are various standards to select from, it can be overwhelming. This article will provide a comprehensive explanation of NSF certification.

What Is NSF Certification?

NSF certification verifies that your water filtration system has been tested by an independent third-party organization. The manufacturer's claims about contaminant removal have been confirmed. The water filter's construction also meets acceptable standards to prevent contamination of your water.

Is ANSI The Same As NSF?

ANSI and NSF aren't the same. NSF is a certification body that is accredited by ANSI. Both organizations produce standards for public health and water filtration. However, they are two separate entities.

NSF Standards For Drinking Water

Contaminants in drinking water can pose a serious health threat or affect its taste and odor. The NSF has established standards based on potential health and aesthetic effects.

NSF 42

NSF 42 sets a minimum standard for reducing non-health related contaminants in water. These contaminants can affect the taste, odor, and color of the water.

NSF 42 is applicable to both point-of-use filters and point-of-entry, whole-house filtration systems. These systems reduce the presence of contaminants such as chlorine, chloramine, particulate, iron, manganese, zinc, and TDS to improve the taste and smell of water.

NSF 53

NSF 53 focuses on reducing health-related contaminants. It targets over 50 contaminants including lead, Cryptosporidium, VOCs, and chromium.

NSF 53 certification is available for both whole-house and point-of-use water filters. The certification also covers construction integrity and materials.

NSF 401

NSF 401 sets a minimum standard for reducing emerging contaminants, including pesticides, herbicides, and pharmaceuticals. This standard is important because there is limited research on the health impact of these chemicals.

82% of consumers are concerned about the presence of these contaminants in water. NSF 401 certified filtration systems can reduce 15 contaminants, including DEET (found in bug spray), ibuprofen, and Bisphenol A (BPA).

NSF 473

NSF protocol 473 was created to address the growing concern of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), which have become common contaminants in groundwater.

NSF 53 Update

Aquasana drinking water filters were the first to receive certification under NSF protocol 473 when it was introduced in 2016. However, in May 2019, NSF 53 was updated to include PFOA and PFOS due to the increasing number of communities affected by these contaminants.

Table of Contaminants and Standards

Are you concerned about a particular contaminant in your drinking water? Refer to the table below to determine the required NSF Standard for your water filtration system.

Aesthetic Impurities:

ChlorineNSF 42
TasteNSF 42
OdorNSF 42
ParticulatesNSF 42

Health Effects:

CryptosporidiumNSF 53
GiardiaNSF 53
LeadNSF 53
Pentavalent ArsenicNSF 53
MercuryNSF 53
PesticidesNSF 53
HerbicidesNSF 53
BenzeneNSF 53
RadonNSF 53
TrihalomethanesNSF 53

Emerging Contaminants:

PharmaceuticalsNSF 401
MeprobamateNSF 401
PhenytoinNSF 401
AtenololNSF 401
CarbamazepineNSF 401
MetolachlorNSF 401
TrimethoprimNSF 401
IbuprofenNSF 401
NaproxenNSF 401
EstroneNSF 401
Bisphenol A (BPA)NSF 401
LinuronNSF 401
NonylphenolsNSF 401

NSF Standards For Water Filtration Systems

The NSF/ANSI standards for contaminant reduction work in tandem with a set of standards that certify individual filtration systems for household use.


NSF/ANSI 44 governs water softeners that reduce hardness, barium, and radium through cation exchange. The standard guarantees minimum efficiency in salt and water consumption.


NSF/ANSI 55 certifies that UV water purifiers effectively remove microbiological contaminants like bacteria and viruses. The standard specifically addresses common contaminants such as Cryptosporidium and Giardia.


NSF/ANSI 58 applies to reverse osmosis systems. The standard requires the demonstration of a reduction in total dissolved solids (TDS). Optional testing is available for claims on contaminants such as arsenic, lead, and fluoride.


NSF/ANSI 62 sets the standard for water distillation systems. It outlines the minimum requirements for design, construction, and performance of these systems to ensure they effectively remove heavy metals, volatile organic compounds (VOCs), and chlorine from water.


NSF/ANSI 177 tests the claims of shower filters regarding chlorine removal and water softening.


NSF/ANSI 244 refers to filtration systems for public water deemed microbiologically safe. These filters provide protection against occasional contamination, ensuring safe drinking water during boil water advisories from the district.


NSF/ANSI P231 tests water purifiers to ensure a minimum reduction in microbiological contaminants such as Giardia and viruses.

NSF Standards For Water Filter Construction

Your water filtration system may have additional NSF certifications. These certifications ensure that the materials used in construction are free from contaminants like lead and plastic that can contaminate your water supply.


NSF/ANSI 61 sets the standards for the minimum impact of chemicals released from materials used in water filtration systems. With NSF 61 certification, you can be assured that the filter media, linings, and seals don't release harmful chemicals like BPA into your water.


NSF/ANSI 372 is a standard that sets the minimum lead content for materials used in water filters and softeners, as well as plumbing components such as pipes, valves, and faucets.

Understanding NSF Certification

It's crucial to comprehend the NSF standard's limitations. NSF 53 certification for a water filter doesn't guarantee that it removes all contaminants listed in the standard.

Instead, the manufacturer's claims about reduction are independently verified.

A NSF 53 water filter may remove 99.9% of chlorine while another only removes 66%. The filter may remove iron up to 3 PPM or up to 15 PPM.

Therefore, it is important to be aware of both the claims made by the water filter and its NSF certification. This combination gives an idea of contaminant reduction.

NSF Standards and Classes

NSF standards define the contaminants removed and verify the construction quality of water filters, including UV purifiers and Reverse Osmosis systems. To help consumers understand the products, these standards are divided into classes.

For instance, NSF 42 has six classes based on the filter's micron rating. Class I filters have a rating of 0.5 – 1 microns, while Class IV filters have a rating of 50+ microns.

NSF 55, which is the standard for ultraviolet water treatment, has two classes. Class A purifiers have a higher intensity of 40 mJ/cm2 and are designed to disinfect water and remove Cryptosporidium and Giardia. Class B systems have a lower intensity of 16 mJ/cm2 and are sufficient for treating water already declared safe by local authorities.

How Does the NSF Water Filter Certification Process Work?

The NSF water filter certification process involves a technical evaluation and independent laboratory testing. The technical evaluation assesses the structural integrity of the system, while laboratory testing confirms the manufacturer's claims about contaminant reduction. NSF also audits the production facility to ensure safe standards are applied in the construction of the filtration systems.

Cost of NSF Certification

The cost of NSF certification varies and can range from $1500 to $100,000. The amount depends on the testing requirements for the product. To gain NSF certification, a product must pay registration fees, application fees, and laboratory testing fees. Additionally, location auditing requires additional fees.

Is it Safe to Use a Filter that Isn't NSF Certified?

Not all water filters are NSF certified, but that doesn't necessarily mean they are unsafe. NSF certification can be costly, so some manufacturers may not seek it even though their products meet the required standards.

To ensure safety, consider choosing filters from well-established brands that have had their products tested by independent third-party laboratories to NSF standards. An example of such a brand is Spring.

Other Certification Agencies

NSF/ANSI isn't the only organization offering certification for water filtration systems. The Water Quality Association (WQA) and the International Association of Plumbing and Mechanical Officials (IAPMO Group) also certify the standards of water filters.

Water Quality Association (WQA)

Water Quality Association (WQA) is a non-profit organization that represents the water treatment industry. They provide consumers with peace of mind through their Gold Seal program. The Gold Seal verifies that water filter system manufacturers' claims are accurate, the product is made of safe materials, and the filter system is durable enough to withstand everyday use.

WQA's Gold Seal program is highly respected in the industry and can be considered as a combination of NSF certification for contaminant reduction and filter system construction. This ensures that consumers can trust the quality and performance of water filter systems with the Gold Seal.

International Association of Plumbing and Mechanical Officials (IAPMO)

The International Association of Plumbing and Mechanical Officials (IAPMO) is a plumbing and mechanical product certification agency that is accredited by the American National Standards Institute (ANSI). It independently tests water filtration systems according to NSF and WQA standards, including NSF/ANSI 42 (taste and odor) and NSF 53 (health effects). IAPMO also provides its own certification.

NSF Certification FAQ

Your final questions about NSF Certification, answered.

How Do I Know if My Water Filter is NSF Certified?

To determine if your water filter is NSF certified, look for the NSF certification mark. This should be displayed prominently on the packaging, the manufacturer's website, and list the relevant NSF standards met by the filter. To verify the certification, you can also search for the product in the online NSF directory.

Is NSF Certification Mandatory?

NSF certification is optional. The Environmental Protection Agency (EPA) doesn't require third-party testing for point-of-use water filter systems.

Does NSF Certification Guarantee My Water is Safe to Drink?

NSF certification doesn't guarantee that your water is safe to drink. It only verifies that the manufacturer's claims about the contaminants that their filter system can remove are accurate. For instance, NSF 42 only certifies the removal of contaminants that affect the appearance of drinking water. It does not address the presence of heavy metals or microbiological contaminants that can make water unsafe for consumption.

Final Thoughts

If your iron removal water filter fails, you'll quickly notice rust-colored drinking water. However, there's no sure sign if the filter isn't working if it's supposed to remove bacteria, pesticides, and heavy metals.

Third-party testing is crucial for your filtration system's peace of mind. You need to be sure the filter removes all contaminants and that the build quality prevents new contaminants from entering the system.

Certification from organizations such as NSF, WQA, or IAPMO is up to you. These organizations have lab testing to support their certification and are trusted.

NSF has a comprehensive range of standards and constantly updates and assesses them, making them the leader in safe drinking water standards.

Eric Phillips

Meet Eric, the Water Treatment Specialist and founder of Dripfina, where he shares his wealth of expertise. With notable features in Realtor, ApartmentTherapy, FamilyHandyMan, and more, Eric is a renowned expert in water treatment industry. Join Eric on Dripfina and benefit from #AskDripfina community to make informed decisions for clean, refreshing water.

Leave a Comment