Seeing “NSF/ANSI 42 certified” on a water filter can sound like a broad assurance about everything the product can reduce. It isn't. The designation has a more specific meaning: the applicable product has been certified for particular requirements and claims under NSF/ANSI 42.
NSF/ANSI 42 primarily addresses aesthetic effects—non-health-related characteristics of drinking water such as chlorine taste and odor. However, simply seeing “NSF 42” does not tell you which individual claims are certified.
To understand what an NSF certification actually tells you, look at three things: the standard, the exact product or configuration, and the specific certified claims shown in its listing.
What Is NSF/ANSI 42?
NSF/ANSI 42, formally titled Drinking Water Treatment Units – Aesthetic Effects, establishes requirements for drinking-water treatment systems designed to reduce non-health-related contaminants and characteristics.
The standard applies to point-of-use and point-of-entry treatment systems. Its scope includes requirements related to material safety, structural integrity, and specific aesthetic-related contaminant-reduction claims. The claims vary from one certified product to another.
Claims that can fall under NSF/ANSI 42 include:
- Chlorine reduction
- Taste and odor reduction
- Chloramine reduction
- Particulate reduction
- Iron reduction
- Manganese reduction
- Zinc reduction
- Certain total dissolved solids (TDS) claims
This does not mean every NSF/ANSI 42-certified product is certified for all of these claims. The individual product's certification listing identifies the claims that actually apply.
What Does “Aesthetic Effects” Mean?
In water treatment, aesthetic effects generally refer to characteristics that affect how water tastes, smells, or looks rather than contaminants addressed primarily because of health effects.
Chlorine is a familiar example. Chlorine is widely used in municipal drinking-water treatment, and residual chlorine can affect the taste or odor of tap water.
This is why NSF/ANSI 42 should not automatically be interpreted as a health-effects certification. NSF distinguishes Standard 42 from standards such as NSF/ANSI 53, which addresses specific health-effects-related contaminant-reduction claims.
For example, if a product is certified under NSF/ANSI 42 for chlorine reduction, that certification supports the applicable chlorine-reduction claim. It does not automatically establish NSF certification for lead, PFAS, pesticides, or other substances that may be discussed elsewhere in the product's performance information.
The individual product listing is what tells you which claims have actually been certified.
What Types of Claims Can Fall Under NSF/ANSI 42?
NSF/ANSI 42 covers several categories of aesthetic-related performance, but certification is not an all-or-nothing designation.
One filter might be certified for chlorine reduction and taste and odor reduction. Another might have additional certified claims such as chloramine or particulate reduction. The exact claims depend on the individual product's certification.
This becomes particularly important when a filter's product information lists numerous substances. A filter may have an NSF/ANSI 42-certified claim for one substance while performance information for another is supported by separate laboratory testing.
Read the certification at the claim level, not just the standard-number level.
How Does NSF/ANSI 42 Certification Work?
An important distinction is the difference between testing and certification.
Testing measures how a product performs under defined conditions. Depending on the test, those conditions can include the substance being challenged, its concentration, water characteristics, flow rate, capacity, and other parameters.
Certification involves evaluation against the applicable requirements of the standard and certified claims. An official certification listing then identifies the applicable product and claims.
A manufacturer may also have independent laboratory testing showing that a particular filter reduced a substance under specified conditions. That information can be useful, but the laboratory result does not automatically make that substance a basis for one of the product's NSF/ANSI 42-certified claims.
“NSF Certified” vs. “Tested to NSF/ANSI 42”
These phrases should not be treated as interchangeable.
When a product is certified, there should be an applicable certification listing identifying the product and relevant certified claims.
By contrast, “tested to NSF/ANSI 42” describes testing and does not, by itself, establish that the product has been certified.
If you encounter a “tested to” statement, look for details such as:
- Who performed the testing?
- What exact product or filter element was tested?
- Which substance or performance characteristic was evaluated?
- What test conditions were used?
- What result was achieved?
- Does the test apply to the same product configuration being sold?
Those details provide considerably more information than the phrase “tested to NSF standards” on its own.
Also remember that NSF is not the only organization that can certify products to NSF/ANSI standards. Other accredited certification organizations may certify qualifying products to applicable NSF/ANSI standards.
NSF/ANSI 42 vs. NSF/ANSI 53: What's the Difference?
NSF/ANSI 42 and NSF/ANSI 53 are both drinking-water treatment standards, but their primary focus differs.
| Standard | General Focus | Examples |
| NSF/ANSI 42 | Aesthetic effects | Claims such as chlorine, taste and odor, particulate, or chloramine reduction where specifically certified |
| NSF/ANSI 53 | Health-effects-related claims | Specific health-effects contaminant-reduction claims where certified |
One standard should not simply be described as “better” than the other. They address different types of performance claims.
More importantly, certification under NSF/ANSI 42 does not automatically mean the product is certified under NSF/ANSI 53.
When comparing filters, check the exact standard and individual claims listed for the product rather than assuming one NSF certification covers another.
NSF/ANSI 42 vs. NSF/ANSI/CAN 372
NSF/ANSI 42 and NSF/ANSI/CAN 372 address different aspects of drinking-water products.
| Standard | Primary Focus | What It Addresses |
| NSF/ANSI 42 | Aesthetic effects | Specific aesthetic-effect performance claims |
| NSF/ANSI/CAN 372 | Lead content | Lead content of applicable drinking-water system components |
NSF/ANSI/CAN 372, Drinking Water System Components – Lead Content, concerns the amount of lead in applicable components.
NSF/ANSI/CAN 372 certification does not mean that a filter is certified to reduce lead from water.
A water-treatment product can therefore have an NSF/ANSI 42 certification for specified aesthetic-effect claims and also meet NSF/ANSI/CAN 372 lead-content requirements. Those address two different questions.
If you want to know whether a filter has a certified lead-reduction claim, a 372 listing by itself does not provide that answer.
Why NSF Certification and Independent Laboratory Testing Are Different
A filter can have both certified performance claims and separate laboratory test results. Both can provide useful information, but they should not be presented as though they are the same thing.
It helps to separate performance information into three categories:
- Official certification listings — identify the applicable standards, products, configurations, and certified claims.
- Independent laboratory testing — shows how a particular product performed under the conditions of a particular test.
- Manufacturer-provided information — may include additional specifications, performance data, instructions, and product claims.
The evidence should also apply to the specific product, filter element, and configuration under consideration. Testing or certification for one filter should not automatically be attributed to another simply because it uses the same brand name.
How to Verify Exactly What a Water Filter Is Certified For
Start with the official certification listing, rather than relying only on an NSF logo or a general statement that a product is “NSF certified.”
1. Find the Exact Product
Search for the manufacturer's name and exact product or model. For replacement filters, identify the specific filter element or cartridge.
2. Confirm the Standard
Identify which standard or standards are associated with the product. Depending on the product, you may encounter standards such as NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 401, or NSF/ANSI/CAN 372.
The standard identifies the applicable category of requirements. It does not necessarily tell you every certified claim.
3. Read the Specific Certified Claims
This is one of the most important steps.
If a listing identifies Chlorine Reduction and Taste and Odor Reduction, those are the claims shown for that product. Other substances discussed in the manufacturer's literature should be evaluated according to the evidence supporting those particular claims.
4. Check the Filter Element and Configuration
Read the details and footnotes attached to the listing. They may identify the filter element, system configuration, service cycle, flushing requirements, or other conditions associated with the certification.
5. Check the Current Listing
Certification information can change. An old article, screenshot, review, or product page should not automatically be treated as proof of a product's current certification status.
For current information, check the applicable official NSF product listing.
Are Berkey® Water Filter Systems NSF/ANSI 42 Certified?
Specific Berkey® configurations are currently listed under NSF/ANSI 42 when equipped with Phoenix Gravity New Millennium Edition™ Filter Elements.
The current NSF listing for New Millennium Concepts Ltd. identifies:
| Berkey System | Filter Element | NSF/ANSI 42 Claims | Service Cycle |
| Big Berkey® | Phoenix Gravity New Millennium Edition PGF9-2 | Chlorine Reduction; Taste and Odor Reduction | 1,050 gallons |
| Royal Berkey® | Phoenix Gravity New Millennium Edition PGF9-2 | Chlorine Reduction; Taste and Odor Reduction | 1,050 gallons |
| Travel Berkey® | Phoenix Gravity New Millennium Edition PGF9-2 | Chlorine Reduction; Taste and Odor Reduction | 1,050 gallons |
This wording is important. It is more precise to say that the Big Berkey®, Royal Berkey®, and Travel Berkey® configurations featuring the specified Phoenix Gravity Elements are currently listed for the applicable NSF/ANSI 42 claims than to make the broad statement that “Berkey is NSF certified.”
The certification should not automatically be extended to other Berkey systems, Black Berkey® Elements, or other filter configurations unless those exact products and configurations appear in the applicable current listing.
What Does NSF/ANSI 42 Certification Mean for Berkey® + Phoenix?
For the currently listed Big Berkey®, Royal Berkey®, and Travel Berkey® configurations featuring the Phoenix Gravity New Millennium Edition Filter Element PGF9-2, NSF's listing identifies:
- Chlorine Reduction
- Taste and Odor Reduction
- 1,050-gallon service cycle
Those are the relevant NSF/ANSI 42 claims shown in the current listing.
Phoenix Gravity Elements also have additional contaminant-reduction testing. Those results should be evaluated separately rather than automatically being described as NSF/ANSI 42-certified claims.
For example, if Phoenix test documentation provides results for substances such as PFAS, lead, heavy metals, VOCs, pharmaceuticals, or disinfection byproducts, the appropriate question is:
What evidence supports this particular claim?
For broader information on Phoenix contaminant testing, see our Phoenix Gravity Filter Test Results.
The Big Berkey®, Royal Berkey®, and Travel Berkey® configurations featuring Phoenix Elements also appear in the applicable NSF lead-content listing. Remember that this relates to lead content in applicable components and should not be described as a certified lead-reduction claim.
How to Compare Water Filters Using NSF Certification
Don't compare water filters based only on whether an NSF logo appears on the packaging or product page. Compare the specific product, standard, and certified claims.
A useful checklist is:
- Which NSF/ANSI standard is listed?
- What specific performance claim is certified?
- Which filter element or cartridge is covered?
- Which system configuration is listed?
- What service cycle or other conditions apply?
- Are additional performance claims supported by certification or separate laboratory testing?
- Is the certification listing current?
Two filters can both carry NSF-related certifications while having different certified claims. Reading the actual listing makes the comparison much more meaningful.
Frequently Asked Questions
What does NSF/ANSI 42 mean?
NSF/ANSI 42 is a drinking-water treatment standard focused primarily on aesthetic effects. Products can be certified for specific claims under the standard, such as chlorine reduction or taste and odor reduction. The exact certified claims vary by product.
What does NSF 42 remove?
There is no single list that every NSF/ANSI 42-certified filter reduces. The standard can include claims such as chlorine, taste and odor, chloramine, particulate, iron, manganese, zinc, and certain TDS claims. Check the individual product listing to see which claims are actually certified.
Does NSF 42 mean a filter reduces chlorine?
Not automatically. Chlorine reduction is a claim that can be certified under NSF/ANSI 42, but you should check the product's listing to confirm whether that specific claim applies.
What is the difference between NSF 42 and NSF 53?
NSF/ANSI 42 primarily addresses aesthetic effects, while NSF/ANSI 53 addresses specific health-effects-related contaminant-reduction claims. Certification under one standard does not automatically mean certification under the other.
What is the difference between NSF 42 and NSF 372?
NSF/ANSI 42 addresses specific drinking-water treatment performance claims related to aesthetic effects. NSF/ANSI/CAN 372 addresses lead content in applicable drinking-water system components.
Does NSF/ANSI/CAN 372 mean a filter removes lead?
No. NSF/ANSI/CAN 372 concerns lead content in applicable product components. It does not, by itself, establish a lead-reduction claim for the water passing through the filter.
Are Berkey® water filters NSF/ANSI 42 certified?
The current NSF listing identifies the Big Berkey®, Royal Berkey®, and Travel Berkey® featuring Phoenix Gravity New Millennium Edition Filter Elements PGF9-2 under NSF/ANSI 42 for Chlorine Reduction and Taste and Odor Reduction, with a listed service cycle of 1,050 gallons.
Are Black Berkey® Elements NSF/ANSI 42 certified?
Do not assume the current certification for Berkey systems featuring Phoenix Gravity Elements applies to Black Berkey® Elements. Certification applies to the specific products and configurations identified in the official listing.
Does Phoenix testing for PFAS or lead mean those claims are NSF/ANSI 42 certified?
Not necessarily. Separate laboratory testing and NSF certification are different forms of evidence. Check the official NSF listing to determine which claims are part of the certification and review the applicable laboratory reports for additional performance data.
Read the Listing, Not Just the Label
NSF/ANSI 42 certification applies to specific products and certified claims. Seeing the standard number on a product does not mean every performance claim associated with that product has been certified under NSF/ANSI 42.
The same principle applies to NSF/ANSI/CAN 372: it concerns lead content in applicable drinking-water system components, not whether a filter reduces lead from water.
For the current Berkey® configurations featuring Phoenix Gravity New Millennium Edition Filter Element PGF9-2, the NSF/ANSI 42 listing identifies Chlorine Reduction and Taste and Odor Reduction, with a 1,050-gallon service cycle for the Big Berkey®, Royal Berkey®, and Travel Berkey®.
So, rather than asking only whether a water filter is “NSF certified,” ask the more useful question:
What, exactly, is this product certified for?