What are NSF Certified Water Filters?

NSF certification is the gold standard for water treatment, but it’s also difficult to achieve. How do NSF standards translate to filtration performance? Is there a difference between certification and testing to NSF standards? Why do some companies forego certification? Here’s everything you need to know about these standards, so you can make an informed decision when you buy your next water filter.

Glasses with used and new water filters on wooden background

NSF and NSF/ANSI Water Treatment Standards are Designed to Meet 5 Criteria

The contaminant reduction claims are valid through the life of the filter.
The parts that make up the filter don’t leach harmful chemicals into the water.
The filter system is structurally sound.
The claims on product labeling, advertising, and literature are accurate and don’t mislead consumers.
The manufacturing methods and materials used have not changed since testing, so consumer products deliver the same performance as tested filters.

How are Products Certified?

The company submits an application that includes a parts list, user information and drawings. The application is reviewed by a team at NSF, and sample products are requested for testing. If the samples pass, NSF representatives audit the manufacturing facility and confirm product information.

This ensures production versions are identical to the tested sample products. The product undergoes a final technical evaluation. If it passes, it’s certified. Once the product is approved, the company’s facilities are audited every year to ensure the products maintain performance.

What’s the Difference Between “NSF Certified,” “Tested According to NSF standards” and “Certified to NSF Standards?”

NSF certified filters are tested by a third party according to NSF regulations. These products can use the NSF seal on their packaging, and their approval status is listed on the NSF website.

Other phrases like “certified to NSF standards” mean the product was tested according to the standard, but it wasn’t done by an approved third party. Naturally, any company doing internal testing is going to have biased results.

Even if the filter was tested by an outside company, there’s no way to tell if testing was conducted through the filter’s life, or it’s identical to the production filter. Even if a filter meets testing requirements when it’s new, performance may drop off or the filter will leach chemicals as it gets older.

Are Water Filters Legally Required to be NSF Certified?

The CDC and most state and local health departments recommend buying NSF certified filters. However, certification isn’t required. Small manufacturers often don’t certify their products, because it’s expensive.

California and Iowa have laws that require third party testing of water treatment products before they can be sold in these states. While they don’t always specify NSF testing, this is the de facto standard used by manufacturers.

What NSF Certifications Cover Water Filters?

NSF/ANSI 42: Removal of aesthetic components, including chlorine and chloramine

Most water pitcher filters are only certified to this standard.
NSF/ANSI 44: Caton resin exchange systems that use sodium chloride or potassium chloride

All salt-based ion exchange water softeners fall under this category.
NSF/ANSI 53: Minimum requirements for materials, design, construction and performance of both point of entry (POE) and point of use (POU) water treatment systems

This mostly covers under sink carbon filters, including stand-alone units and those that are part of a reverse osmosis system. Manufacturers must specify which contaminants are removed under this standard. For example, “NSF/ANSI 53 Certified to Remove Lead” means the filter lowers lead contamination to 5 ppb or less. However, it doesn’t mean the filter removes chlorine, another contaminate covered by this standard. This standard sets minimum performance requirements. You should always check test results provided by the manufacturer for real world performance.
NSF/ANSI 55: UV water treatment

Systems that meet this requirement deliver 40mJ of UV light, making them effective at killing 99.99% of pathogens in drinking water.
NSF/ANSI 58: Material safety, structural integrity and contaminate reduction of reverse osmosis filters

This standard includes the removal of nitrates, nitrides, and heavy metals.
NSF/ANSI 62: Water distillation

While this test includes several contaminates, systems only need to treat one or more contaminates to meet requirements. Testing is based on processing municipal or private well water, not heavily contaminated water.
NSF/ANSI 177: Chlorine-removing shower filters
NSF/ANSI 244: Removal of accidental microbiological contamination

This applies to a wide range of treatment systems, including filters and reverse osmosis.
NSF/ANSI 401: Removal of emergent or incidental compounds

This identifies filters that may remove pharmaceuticals, herbicides, pesticides, flame retardants and detergents. While this covers a wide range of possible contaminates, the test looks for 15 common chemicals. Carbon block, activated carbon and reverse osmosis filters may fall into this category.
NSF P477: Cyanotoxin removal

Cyanotoxins are commonly called “blue-green algae.” Testing availability is limited, so this is only used on point of use systems. It may expand to point of entry systems in the future.
NSF P427: PFOS and PFOA removal

These chemicals are out of production, but they don’t break down naturally, making them a health concern. Testing mostly covers point of use and countertop systems.
NSF/JWPA P72: Radioactive iodine

This standard was developed in cooperation with the Japan Water Purification Association (JWPA) after the Fukushima disaster in 2011. An earthquake released radioactive iodine, which can collect in the thyroid and cause cancer. Activated carbon, ion exchange and reverse osmosis systems can be tested for their effectiveness under this standard.

Who are NSF and ANSI?

Founded in 1944 as the National Sanitation Foundation, this non-profit organization changed their name to “NSF” when their scope extended to a range of products. Today, they provide standards and consumer education for food, water, automotive, aerospace, health care and construction products.

Although they started in America, this group currently operates in over 180 countries. The NSF released their first water filtration standard in 1973. Since then, they’ve expanded their testing to cover a wide range of home water filtration products with constant updates to address new technologies and breakthroughs in health research.

Most NSF water treatment standards are also approved by ANSI, the American National Standards Institute. Like NSF, they create standards for a wide range of products. Standards developed collaboratively by the NSF and ANSI are labeled “NSF/ANSI.”

Together, these agencies work with people involved in all aspects of the industry to develop standards. This includes industry representatives, government agencies, health officials, academic partners and regular citizens.

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