ANSI/NSF: What’s it all about?

by Gene Franks

Editor’s Note:  This article first appeared in the Pure Water Occasional for April 2010. It has since been expanded.


A standard question about water treatment products these days is to ask if they are “NSF certified.” For our products, the answer isn’t simple. Some of them carry full third-party certification obtained by the manufacturer, some have certification on some of their components, and some aren’t certified at all. And some have certification from third parties that have no affiliation with NSF.

“Is your product NSF certified?”  implies–and most take it to mean–that there is some federally sponsored (N for national) certifying agency, probably a branch of the EPA, that  “certifies” products the way that USDA puts its stamp on the rump of a dead pig making it an officially edible ham.  That isn’t the way it works at all.

First, NSF isn’t a government agency.  NSF used to stand for National Sanitation Foundation, but it is my understanding that the letters don’t “stand for” anything now, and the corporate name is simply NSF, a.k.a. NSF International.  NSF started in 1944 when a couple of University of Michigan professors saw a need to set up safety standards for lunch counters and took it upon themselves to start such a service as a university activity.  The agency over the years separated from the university and  grew into a very large and well funded non-profit corporation.

So, how did NSF get the right to dictate “standards” for water treatment devices (and a host of other commercial products)?


Actually, it didn’t.   ANSI, the American National Standards Institute,  is the official certifying agency in the US.  (Canada has its equivalent in the Standards Council of Canada,  SCC.)   The US EPA, Health Canada, as well as all states of the US and all provinces of Canada rely on ANSI and SCC to determine the standards that are accepted for third party certification of products.

So, where does NSF fit in?  NSF plays a double role in the certification process.  First, it “authors” standards, at ANSI’s behest, and it is also one of the many agencies that are licensed to perform the testing that is required in the standards for product certification. ANSI/NSF standards are standards prepared by NSF under the authority and approval of ANSI.

NSF is only one of many agencies that are authorized to test products to the standards set by NSF/ANSI.   Others that are equally empowered to perform the rites of certification include the Water Quality Association (WQA), Underwriter Laboratories (UL), the Canadian Standards Association (CSA), Truesdail Laboratories, Mechanical Officials, and the International Association of Plumbing, and more.

So, when a product is said to be “tested to ANSI/NSF” standards, this means that the product has been tested to standards authored by NSF for ANSI and tested by either NSF or another ANSI-approved testing agency (like the WQA), or even tested by a non-certified third party tester using NSF/ANSI standards.

Something that is often not understood is that if you want to research a product’s certification, you must know the testing agency.  The NSF website lists only products tested by NSF’s testing division.  Products tested to NSF standards by, for example, the International Association of Plumbing, are not listed on NSF’s website. There is no central registrar for all NSF/ANSI tested products.  Each testing agency keeps its own records.  If a product advertiser claims “NSF certification” and you go to NSF’s website for verification and can’t find it, it doesn’t mean that the advertiser is (or isn’t) lying.

What All This Means

There is much confusion in the public mind about what “NSF Certification” means.  What it does not necessarily mean is that the certified product is “guaranteed to work,” or that a level of performance is guaranteed.  There are numerous NSF/ANSI standards that apply to water treatment products.  Not all address performance, although advertisers frequently imply that superior performance is guaranteed simply because their product is “NSF certified.” Certainly this misconception is common among consumers.

Here are the standards that water treatment devices are most frequently tested and certified under:

STANDARD 42: Drinking Water Treatment Devices – Aesthetic Effects

STANDARD 44: Cation Exchange Water Softeners

STANDARD 53: Drinking Water Treatment Devices – Health Effects

STANDARD 55: Ultraviolet Microbiological Water Treatment Systems

STANDARD 58: Reverse Osmosis Drinking Water Treatment Systems

STANDARD 62: Drinking Water Distillation Systems

And the most recent: STANDARD 401: Emerging Contaminants.

Most manufacturers of water treatment devices present their certification information in a straightforward manner that really tells you what their certification covers.  As an example, here’s how KX Industries (a.k.a. Filtrex, the nation’s largest maker of extruded carbon block filters) labels one of our favorite products, the MatiriKX PB1 filter cartridge. KX displays this certificate on the product’s fact sheet:

The MATRIKX® + Pb1 is
Tested and Certified by
NSF International under
NSF/ANSI Standard 42
for material
requirements only.


What this says is that NSF International (the testing branch of NSF) has performed the necessary tests to certify the product under the materials requirements only of Standard 42 prepared by NSF for ANSI.  The materials requirement under Standard 42 gives you the assurance that the materials used in the product are safe and non-toxic and that the cartridge isn’t adding anything to the water that will cause harm.   Standard 42 materials certification makes no guarantee of performance.  It does not speak to the product’s ability to remove chlorine, lead, or arsenic. It just tells you that it won’t put lead, arsenic or formaldehyde into the water.
Note that this is a “component” certification, not a product performance certification.

When looking at water treatment products, some are certified and marked with the word “component” on the product label.  There is a difference between system certification and component certification. A component is an individual piece of a system and requires less rigorous testing for certification. A certified filter cartridge (component) could be put into a reverse osmosis unit (product) with a cheap faucet that leaches lead into the water.

The testing a component must undergo to pass requirements for certification include material safety and structural integrity if it is a pressure-bearing component. The material safety test ensures no contaminants are introduced into the the water.The structural integrity test ensures no leaking will occur when exposed to high pressure or repeated fluctuations in pressure.

System certification includes the aforementioned testing as well as meeting performance criteria. Performance testing must meet the minimum criteria which includes “testing of minimum and rated service flow rates, testing of pressure drop for larger products, and evaluating product design to ensure replacement components are readily removable, waste connections have an appropriate air gap, and the product does not pose obvious hazards.” Each system may be subject to more rigorous testing requirements as well.

Carrying products that are system or component certified assures the seller and consumer that these water treatment parts will not leak or put contaminants into the water.

In addition to this actual certification, the manufacturer’s sheet for the PB1 cartridge informs that lead reduction, chlorine, taste/odor, turbidity and cyst reduction claims are “based on NSF/ANSI Standard 53.” (Since this article was written, the PB1 spec sheet now includes performance data for reduction of PFAS, Chloramine, and VOC as well.) This means that KX didn’t actually submit the cartridge for NSF/ANSI certification under Standard 53 (a health effects performance standard) but that it was tested (by KX or an unspecified third party) and found to perform at the specified levels as determined by NSF/ANSI Standard 53.  (In the case of the PB1, an additional label indicates that the testing to NSF/ANSI standards was done by the Water Quality Association’s testing division.)

Why  would KX Industries not just have its PB1 cartridge NSF/ANSI certified? Well, cost for one thing. It costs literally tens of thousands of dollars to obtain and maintain NSF/ANSI certification on a single product.  But also because it is a “component” rather than a full product, like an RO unit.  Common sense tells you that no matter how good the filter cartridge or the RO membrane, if you put it into a poorly manufactured, defective end product it will not produce a good result.  As a single example, no matter how good a filter cartridge is, if it is put into an inferior undersink water filter with a cheap faucet that leaches lead into the water, the cartridge certification means nothing. Performance certification has to be done for the entire device, not the individual components.

Many manufacturers use certification as a selling tool.  They spend  large amounts maintaining product certification and they advertise their products accordingly, often with the implication that uncertified products are not to be trusted.  Other manufacturers–KX Industries, for example, as well as many other highly respected manufacturers–rely as much on their own reputation and experience as third-party certification to sell their products.  The lower price they are able to charge because of the the money saved on certification gives an added selling advantage.

Certification is important.  It gives the customer confidence that the product meets a certain standard–either in materials it is made from or in its performance.  But if you limit yourself to products that are NSF/ANSI certified you may be depriving yourself of some really superior products as well as spending more than you need to.

“Let the buyer beware” is a two-edged sword.  It isn’t good to buy an inferior product, but no one likes the idea of paying an extra $30 for a filter cartridge to support the manufacturer’s advertising campaign.

Source: Pure Water Occasional.