ANSI/NSF: What’s it all about?

by Gene Franks

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, 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, among others.

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.”

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


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, 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.  (If Chinese toys were certified under this standard, you could let your child gnaw on them without concern.) Standard 42 materials certification makes no guarantee of performance.


In addition to this actual certification, the manufacturer’s sheet informs that lead reduction, chlorine, taste/odor, turbidity and cyst reduction claims are “based on NSF/ANSI Standard 53.”  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.

Why  would KX Industries not just have its PB1 cartridge NSF/ANSI certified?  Mainly, the cost.  It costs literally tens of thousands of dollars to obtain and maintain NSF/ANSI certification.  Many manufacturers use certification as a selling tool.  They spend  large amounts maintaining product certification and they advertise their products accordingly, usually 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 more on their own reputation and experience than 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 $20 for a filter cartridge to support the manufacturer’s advertising campaign.