NSF Certified Water Filters: Why It’s Important

NSF Certified Water Filters: Why It's Important

If you’re looking for a water filter, it’s important to know what NSF certification means.

The National Sanitation Foundation (NSF) is an independent organization that tests and certifies water treatment equipment. Their certification program provides independent third-party verification of product claims to ensure they are accurate and meet strict standards for material safety and performance.

It’s also important to note that there are different types of NSF certification depending on what your needs are. For example, if you are concerned about lead or arsenic in your water, you should look for NSF/ANSI standard 53 which addresses contaminants with a health effect.

When you choose a water filter that is NSF certified, you can be sure that you are getting a product of the highest quality.

What is NSFNSF International

NSF is an independent, third-party organization that tests and certifies water treatment equipment. They develop standards for water treatment products and certify them based on their safety and performance.

An important part of their certification is verifying the claims made by manufacturers to ensure they are accurate. NSF rigorously tests products in their labs, using industry standards. They only certify products proven to do what they claim.

NSF is recognized worldwide as a leader in water quality and has been setting standards for water treatment products since 1944. NSF is listed as a World Health Organization (WHO) Collaborating Center for Water Safety and Treatment.

American National Standards Institute and NSF

The American National Standards Institute (ANSI) is an international standards development agency. They develop the detailed requirements that a filter or other treatment system must meet. Their requirements are developed by subject matter experts and are based on industry standards and the state of science.

NSF Standards are recognized by ANSI, which is why you will typically see their certifications listed as NSF/ANSI.

What Are the Different NSF Certifications and StandardsNSF Certificates to Look for

NSF has two NSF standards that apply to drinking water treatment. NSF calls these filters “Drinking Water Treatment Units”. The NSF standards for water filters are:

  1. NSF Standard 42: Aesthetic Effects – this includes chlorine, taste, odor, and particulates.
  2. NSF Standard 53: Health Effects – this applies to contaminants that can cause disease and harm to your health.

Which NSF standard do you need

If you are worried about a particular contaminant, look it up in the following table to see which NSF certification and standard is applicable. For example, chlorine is considered to be an “aesthetic impurity” and is covered by NSF standard 42.

Table 1 – NSF Certifications for Common Contaminants
Contaminant Standard Category
chlorine NSF 42 Aesthetic Impurities
taste NSF 42 Aesthetic Impurities
odor NSF 42 Aesthetic Impurities
particulates NSF 42 Aesthetic Impurities
bacteria NSF 55 Contaminants with a Health Effect
viruses NSF 55 Contaminants with a Health Effect
cycst NSF 55 Contaminants with a Health Effect
Cryptosporidium NSF 53 Contaminants with a Health Effect
Giardia NSF 53 Contaminants with a Health Effect
lead NSF 53 Contaminants with a Health Effect
pentavalent arsenic NSF 53 Contaminants with a Health Effect
mercury NSF 53 Contaminants with a Health Effect
pesticides NSF 53 Contaminants with a Health Effect
herbicides NSF 53 Contaminants with a Health Effect
benzene NSF 53 Contaminants with a Health Effect
MTBE NSF 53 Contaminants with a Health Effect
radon NSF 53 Contaminants with a Health Effect
 trihalomethanes NSF 53 Contaminants with a Health Effect
 PCBs NSF 53 Contaminants with a Health Effect
PFOA NSF 53 Contaminants with a Health Effect
PFOS NSF 53 Contaminants with a Health Effect
pharmaceuticals NSF 401 Emerging Contaminants
meprobamate NSF 401 Emerging Contaminants
phenytoin NSF 401 Emerging Contaminants
atenolol NSF 401 Emerging Contaminants
carbamazepine NSF 401 Emerging Contaminants
tcep NSF 401 Emerging Contaminants
tcpp NSF 401 Emerging Contaminants
deet NSF 401 Emerging Contaminants
metolachlor NSF 401 Emerging Contaminants
trimethoprim NSF 401 Emerging Contaminants
ibuprofen NSF 401 Emerging Contaminants
naproxen NSF 401 Emerging Contaminants
estrone NSF 401 Emerging Contaminants
bisphenol a NSF 401 Emerging Contaminants
linuron NSF 401 Emerging Contaminants
nonyl phenol NSF 401 Emerging Contaminants

NSF also has six standards for water filtration equipment.

  1. NSF/ANSI 44: Water softeners
  2. NSF/ANSI 55: Ultraviolet treatment systems
  3. NSF/ANSI 58: Reverse osmosis systems
  4. NSF/ANSI 62: Distillation systems
  5. NSF/ANSI 177: Shower filters
  6. NSF P231: Microbiological water purifiers

If you are using a particular type of water treatment system, such as reverse osmosis, you can check to see if it carries NSF certification. The following table provides a summary of NSF standards and certifications for water treatment technologies that you may have in your home.

Table 2 – NSF Certifications for Water Treatment Systems
Treatment Technology NSF Certification
Water softeners NSF/ANSI 44
Ultraviolet treatment systems NSF/ANSI 55
Reverse osmosis systems NSF/ANSI 58
Distillation systems NSF/ANSI 62
Shower filters NSF/ANSI 177
Microbiological water purifiers NSF P231

NSF certifications are given for individual standards. The first NSF standard for drinking water was set in 1973.

What Does NSF Certification Actually Mean?NSF Certificate

When you see the NSF certification mark on a product, it means that the product has been independently tested by NSF and meets their strict standards for material safety and performance. It also means that the manufacturer’s claims about the filter’s performance are accurate – and this accuracy is verified with laboratory testing.

Quality materials and construction are

NSF certification indicates that the equipment you’re buying is made with quality materials and construction. This is important, because it means the filter will last longer and perform better. It’s also one less thing you’ll have to worry about – trust that an NSF certified product has been thoroughly tested and is guaranteed to work as promised.

Benefit of NSF certification for you and

When you buy an NSF certified product, you are relying on their rigorous testing and evaluation process. This means that you can be sure the product meets all safety and performance standards and is made of contaminant-free materials. You also know that the manufacturer’s claims about the filter are accurate – so you can feel confident that you’re getting what you pay for.

Having an NSF certified water filter in your home is important for two reasons:

  1. NSF certification guarantees quality materials and construction
  2. NSF certification means the manufacturer’s claims about performance are accurate – backed by laboratory testing.

Cost of certification

Filter manufacturers pay NSF to certify their products. Because the certification process is so thorough and rigorous, the cost of certification can be high.

Depending on the type of filter and the claims the manufacturer makes, NSF certification can cost as much as $100,000. This is a lot of money, especially for a small company or one just starting out.

However, it costs a lot of money to evaluate and verify the claims made about a product. Some of the analytical testing for contaminants can cost hundreds of dollars, and several rounds of testing are required.

How to interpret NSF certification

If a product carries NSF certification, does that mean it removes all of the contaminant? Surprisingly, it doesn’t.

NSF verifies the manufacturer’s claims about contaminant reduction. They don’t necessarily confirm that the filter removes 100% of the chemical.

So, if a manufacturer only claims a 45% reduction in a particular contaminant, you could end up with concentrations above the drinking water standard for that compound.

You have to review what the manufacturer is claiming, especially as it relates to treating contaminants that can have an adverse effect on your health. If they claim that the filter removes all of the contaminant, or at least to levels below the drinking water standard, then you can be confident your family is protected.

Difference Between NSF Standards and Classes


NSF has two standards that apply to contaminants that are removed. These are based on the nature of the compounds – aesthetics versus health effects.

They also have standards that apply to the various types of treatment systems. This covers everything from reverse osmosis filters to UV lights.

NSF Classes

Classes are divisions within the standards. There are several.

For example, Standard 42, mechanical filtration, has six classes. The classes apply to the filter micron rating. Here are the classes for the NSF Standard 42 – filter standard.

  • Class I: ½ -1 micron
  • Class II: 1-5 microns
  • Class III: 5-15 microns
  • Class IV: 15-30
  • Class V: 30-50
  • Class VI: 50+ microns

Other Independent Testing and Certification Agencies

NSF is not the only independent, third-party testing agency. There are others, such as the Water Quality Association (WQA) and Underwriters Laboratories Inc. (UL).

Water Quality Association (WQA)

The WQA is a not-for-profit trade association representing the residential, commercial, and industrial water treatment industry. They have been around since 1958 and have over 3,500 members. WQA offer certifications for products that filter or purify water.

The WQA certified product listings are available to help connect consumers with water treatment products that have been tested and rated according to the highest industry standards. Their Gold Seal Program is one way they do this. All listings have been carefully curated so that your family is always safe and healthy when it comes time for them get their drink on!

International Association of Plumbing and Mechanical Officials (IAPMO Group)

The International Association of Plumbing and Mechanical Officials (IPMO) coordinates the development and adaptation of plumbing, mechanical, swimming pool codes to meet individual needs both in America as well abroad.

IMPO provides code development assistance, education and training, certification for professionals in the industry, product testing and certification, and product evaluations.

What About Non-Certified Filters

Just because a product is not certified, does not mean that it’s unsafe. It could be that the manufacturer has not gone through the process or couldn’t afford the fees.

Obviously, NSF certification is the gold standard. But, if you can’t find a certified filter for your needs, don’t despair.

You can verify the performance of your filter by testing its performance. I wrote an article on this topic that you can read here.

It’s always best to do your research and make an informed decision about what water filter is best for you and your family.


Is it safe to use a filter that isn’t NSF certified?

It could be safe, but you won’t have the same level of assurance as you would with an NSF certified filter. I recommend looking for NSF certified equipment to avoid any problems after you’re bought an installed your treatment equipment.

Is NSF certification mandatory?

No, it isn’t. However, many retailers will only carry products that are NSF certified. It helps us as consumers buy products that have been tested and verified by a trusted organization.

Does NSF certification mean my filter removes all of the lead in my water?

No, NSF certification only ensures that the filter is built to industry standards and meets the manufacturer’s claims. You will still need to have your water tested for lead content.

Does NSF certification guarantee my water is safe to drink?

No, NSF certification only guarantees that the filter is effective at removing certain contaminants from water. It does not guarantee that the water is safe to drink. You will still need to have your water tested for safety.

Final Take on NSF Certification

NSF International is a not-for-profit, public health and environmental organization that has been testing water filters for over 70 years. NSF certification means that a product has met rigorous standards for performance, safety, and contaminant reduction. When you see the NSF mark on a water filter or other product, you can be confident that it meets these high standards.

There are many different NSF certifications and standards, so it’s important to understand what they mean. Not all filters are certified by NSF, but choosing one that is can give you peace of mind knowing that it will meet your needs. If you’re looking for a safe and effective way to reduce contaminants in your drinking water, an NSF certified filter is a great option.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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