Top 8 NSF Drinking Water Filtration Standards

Learn about NSF drinking water standards, certifying bodies like WQA and IAPMO, and what they mean for your drinking water.

By: Kathryn Fisher

When starting your research for your next water filter, you might look to product reviews on Amazon, or create your own product comparison spreadsheet. Maybe you trust water quality dealers, science journals, or research panels. Or maybe you look for certification seals from third-party experts.

The leader in water filtration certification is NSF. NSF establishes drinking water standards and also certifies products to meet those standards. There are other third-party scientific experts like the International Association of Plumbing and Mechanical Officials (IAPMO) and Water Quality Association (WQA) who independently test and certify products to NSF Standards.

“The system you choose impacts the safety of the water you use every day, so it’s important to pick a filter that’s certified to do what it claims.”

The system you choose impacts the health of the water you use every day, so it’s important to pick a filter that’s certified to do what it claims. Read on to learn more about NSF, IAPMO, and WQA; the standards they certify for; and tips to help you determine which water filters are certified and for which standards.

Who is NSF?

NSF is a third-party entity that develops standards for clean water, food, and consumer products. Founded in 1944, their mission is “to protect and improve global human health. Manufacturers, regulators and consumers look to the NSF to develop public health standards and certifications that help protect food, water, consumer products and the environment.”

NSF has developed more than 140 public health standards in over 180 countries, with products ranging from water filters to home furnishings. Products are rigorously tested according to these set standards and certified that they do what they claim. NSF certifications are given perl standard, so a product may be certified for one NSF standard but not have all the available standards. Products may be tested and certified by NSF directly, or can be tested and certified to NSF Standards by other third-party groups like IAPMO and the WQA.

Who is ANSI?

You may see the acronym “ANSI” attached to the end of NSF listings. ANSI, which stands for American National Standards Institute, was founded in 1918 and is a non-profit, private organization that sets testing standards and conformity assessments nationally and internationally. NSF works closely with ANSI to develop the standards to which NSF tests and certifies.

While ANSI does not directly develop the standards NSF tests to, they provide a framework for NSF to ensure the standards are fair and water quality is met.

NSF water filter standards

The first NSF standard for drinking water was set in 1973, but additional standards were added throughout the 1980s and continue to be added today as new information becomes available. Here are the top 8 filtration standards developed by NSF and used by them, IAPMO, and WQA when certifying water filters:

1. NSF Standard 42: Aesthetic Effects

Reduces non-health related contaminants – Chlorine, taste, odor, and particulates that might be in your drinking water.

2. NSF Standard 53: Health Effects

Reduces specific health-related contaminants – cryptosporidium, giardia, lead, and volatile organic chemicals (VOCs). In 2019, NSF Standard P473, which covers the reduction of PFOA/PFOS was incorporated into this standard.

3. NSF Standard 55: Ultraviolet Light

Water filters that use ultraviolet (UV) light can inactivate or kill bacteria, viruses, and cysts in contaminated water or can reduce the amount of non-disease-causing bacteria.

4. NSF Standard 58: Reverse Osmosis

Reduces contaminants that can be removed through reverse osmosis filtration. In order to receive this certification, an RO system must remove TDS. However, the best RO systems remove additional contaminants including hexavalent chromium, cysts, fluoride, arsenic, and nitrates/nitrites.

5. NSF Standard 401: Emerging Compounds/Incidental Contaminants

When a water filtration system removes up to 15 individual contaminants such as prescription drugs, over the counter medications like ibuprofen and Naproxen, herbicides and pesticides, as well as other chemical compounds like BPA.

6. NSF Standard P473: PFOA/PFOS

In 2019, NSF combined Standard P473 into NSF Standard 53, so you may not see it listed for new filters. But in 2016, NSF was the first to develop a standard for the reduction of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate – chemicals used to make non-stick cookware, fire retardant, and more. Aquasana filters were the first to earn certification under this standard. .

7. NSF Standard P231: Microbiological Filtration

Reduces microbial contaminants like viruses and bacteria. This standard was developed to certify microbiological water purifiers to filter and treat water of unknown microbiological quality but are presumed potable. Microbiological water purifiers remove/kill/inactivate types of disease-causing microorganisms from the water. 

8.  NSF Standard 372

This standard verifies that a product is compliant in minimizing lead content. This standard is consistent with the United States Safe Drinking Water Act (SDWA) and its lead-free plumbing requirements. This standard addresses lead content only. For water filters, the more relevant standards are instead related to lead reduction, meaning NSF/ANSI 42, 44, 53, 55, 58, or 62.

Who is WQA?

The WQA was founded in 1974, and “serves as an educator of water treatment professionals, a certifier of water treatment products, a public information resource and the voice of the water quality improvement industry.” They offer testing and certification services for water treatment products to various standards including NSF’s, and their assessment includes lab tests, a literature review, and materials assessment.

Who is IAPMO?

Founded in 1926, the IAPMO Group (or, the International Association of Plumbing and Mechanical Officials) is an independent organization that develops and tests to certain standards, to meet needs both nationally and internationally.

They certify products to externally-mandated standards, like NSF's, and also set some of their own standard for plumbing code requirements, for example.

How to know if a water filter is certified

Water filters can claim to remove or reduce contaminants, but certification from an independent group can give you assurance that the product really does what it says it will. Luckily, you can easily confirm if a water filter is certified by looking for a seal on the product’s label or packaging. The seal may be from the NSF, or another group like IAPMO or the WQA with details about the standards they’ve been tested to. Here’s what the seals look like for each of these groups:

For all NSF certified products, look for the following seal or visit their database.

For all IAPMO certified products, look for the following seal or visit their database.

For all WQA certified products, look for the following seal or visit their database.

To see if a water filter is certified, look for these seals and check which standards they’re certified to. Some water filters may be certified to NSF Standards by other groups, or they can be certified to the testing group’s own standards. Typically, you can find the seal on the bottom of the water filter system on the product sticker. This product sticker will also include the flow rate, manufacturing information, and any electricity specifications. If you’re unable to find the seal directly on the system, check the owner’s manual in the data specifications section and/or the product's Performance Data Sheet. 

How NSF Certifications are obtained for water filtration systems

1. Application

If a company wants to become certified by NSF or to any of the other third-party testing entities, they first must submit an application for the filtration system. This application must include important information about the product materials  such as materials  used to make it, where it is manufactured, and most importantly, what claims the company plans on making regarding contaminant reduction.

2. Testing and inspection

Next, the experts at the testing facility evaluate the filtration system for structural integrity, safety, and filtration efficacy. Through this rigorous testing, they can determine if your filtration system does what it says it’s going to do. This testing includes water pressure tests, contaminant testing, and filter replacement.

During this time, the certifying body must also review any literature that includes their seal. This can be anything from owner’s manuals, to website text, to system labels. All certifying bodies have specific language you can and cannot use when referencing their certification.

3. Certification approval

If the system passes all testing, NSF, IAPMO, or WQA will send the company a certification contract. Once signed and returned, the seal can be used. All certifying bodies also add the filtration system to their website and include the standards the filter met.  

While certifications aren’t required to sell a water filtration system, at Aquasana we believe it’s incredibly important. All of our water filtration systems are third-party or independently tested to meet NSF/ANSI Standards and the vast majority are certified. The cost of getting a filtration system tested and certified by a third party costs upwards of $100,000 per product, so while this is a major cost for our company, we believe that providing peace of mind to our customers that each of our product’s claims are rigorously tested is worth the investment.

Aquasana and certifications

While many companies may claim to reduce contaminants, Aquasana tests and certifies products through NSF, WQA, and IAPMO to various NSF Standards. Here’s an overview of our drinking water filters that are certified to NSF Standards.

Certified under sink and countertop filters

We offer several under sink and countertop systems that are WQA certified to various NSF/ANSI Standards. Our SmartFlow® Reverse Osmosis system is WQA tested and certified to NSF/ANSI standards 42, 53, 58, 401, and CSA 483.1.The Claryum® 3-Stage Max Flow, 3-Stage, 2-Stage Under Sink Filter, and Clean Water Machine are also WQA tested and certified to NSF Standards 42, 53, and 401. Lastly, our Claryum® Direct Connect is IAPMO certified to NSF Standards 42, 53, and 401.

Certified whole house filters

We offer two whole house systems that are WQA certified to NSF/ANSI Standards 42 and 61. Both the Rhino® and Rhino® Max Flow feature a 1,000,000 gallon capacity (or up to 10 years) that reduces 97% of chlorine from every faucet in your home, though the Max Flow offers 2x the flow rate (14 GPM).

If you live in an area where Chloramines are an issue in your water, our Rhino® Chloramines and Rhino® Chloramines Max Flow are tested and certified to NSF Standard 42 to reduce 83% of chloramines and 97% of chlorine. 

And finally, our OptimH2O® is IAPMO tested and certified to tackle lead, cysts, PFOA/PFOS, chlorine and chloramines, making it our most powerful whole house system available. 

Aquasana will continue to lead the industry by engineering and earning our product certifications that meet NSF’s rigorous standards. We will be on guard against whatever pollutants and contaminants are threatening our water, and continue to be the best solution to aging water infrastructure, so you can experience the cleanest, healthiest water, and peace of mind for your whole family.



Tested and certified to reduce lead, cysts, and PFOA/PFOS, plus tackles chlorine and chloramines.