NSF International Certifications Listings

NSF International Certifications Listings

NSF International Certifications Listings are easily confused, and this Bulletin is to help drinking water treatment users understand NSF certifications and listings.

NSF is a not-for-profit corporation founded in 1944 to promote good sanitation. Its main “business” is to bring together experts in public health, manufacturing, and sanitation from government, industry, academia and the public to develop and administer performance standards for products which have some impact on sanitation and public health. NSF maintains state-of-the-art laboratories where products can be tested according to the standards.

Manufacturers voluntarily submit products for evaluation; if they pass the tests, they are “Listed” and certain tested claims are “Certified,” and the products are authorized to display the NSF Seal on labels and literature. Although non-governmental, NSF does have some official status as the lead agency for the testing and approval of both the chemicals used in water treatment and the materials of construction used in drinking water systems, under contract to the U.S. Environmental Protection Agency.

NSF Standards are recognized by the American National Standards Institute and the equivalent organization in the European Community, the Dutch Council for Certification (RvC). Public Health Officials worldwide can take confidence from the knowledge that people like themselves have written and approved these standards, and NSF’s reputation for thoroughness, independence and credibility has made it one of the most trusted public agencies in the world. NSF has also received the distinction of being appointed a Registrar for the International Standards Organization (ISO) and a World Health Organization (WHO) Collaborating Center for Water Safety and Treatment.

There are two NSF Standards for “Drinking Water Treatment Units” (not including others for reverse osmosis, ion exchange, and ultra-violet units): Standard 42 for Aesthetic Effects, and Standard 53 for Health Effects. They are similar, and most of the basic requirements are the same for both.

A water filter which is “NSF-Listed:’ or which has claims which are “NSF-Certified” is one which:
1. is thoughtfully designed and carefully constructed
a) using established water treatment media and methods,
b) using materials of construction which are tested and documented to be appropriate for potable
water use,
c) and is tested and verified to conform to minimum standards of mechanical and hydraulic
d) and is tested and verified to conform to minimum standards of hydraulic functioning (minimum
flow rate, maximum initial pressure drop, reasonable freedom from channeling and dumping),
2. is adequately and truthfully labeled and advertised,
3. is routinely re-tested, and its manufacturing procedures, documentation and facilities
inspected/audited annually, and
4. in addition to the above “good manufacturing practices” required of all Listed products, has
been tested and approved for one or more specific functions which are required to be listed
immediately next to the NSF Seal on labels and literature.

An example of a proper NSF Listing/Certification, of a product with all Everpure claims:

System Tested and Certified by NSF International against ANSI/NSF Standards 42 and 53 for the reduction of:
Standard No. 42: Aesthetic Effects
Chemical Unit
Taste & Odor Reduction
Chlorine Reduction
Chloramines Reduction
Scale and Corrosion Control
Mechanical Filtration Unit
Particulate Reduction, Class I:
99.9+% reduction of particles
½ micron and larger in size

Standard No. 53: Health Effects
Chemical Reduction Unit
Total Trihalomethanes Reduction
Volatile Organic Chemical Reduction
Lead Reduction
Mechanical Filtration Unit
Turbidity Reduction
Cyst Reduction
Asbestos Reduction

1. Standard 42 claims for general mechanical filtration and chlorine/T&O reduction have classes of performance, but for all other claims there is only a pass/fail. For Taste & Odor, the classes represent chlorine reduction efficiency: Class I, a minimum of 75% chlorine reduction; Class II, 50% reduction; Class III, 25%. For mechanical filtration, the classes represent particle size ranges which are removed with a minimum 85% efficiency:

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

1. Note that a Class I or II rating does not imply Cyst Reduction—that requires a 99.95% minimum filtration efficiency for 3-4 micron test dust particles, 3.000 micron micro-spheres, or live Cryptosporidium oocysts.
2. The two organic reduction claims, THM and VOC Reduction, are easy to confuse because the two chemical groups overlap (THMs are VOCs) and because both claims are tested with the same challenge chemical, chloroform. The test for the THM claim documents the gallonage for removing 450 ppb chloroform down to a maximum of 80 ppb (the legal limit in the U.S.), for a minimum removal efficiency of 82%. The test for VOC Reduction documents the gallonage for removing 300 ppb chloroform down to a maximum of 15 ppb at the end, for a minimum efficiency of 95% reduction. VOC Reduction is thus a much stronger claim, but is has only about half the capacity of
THM Reduction.
3. We offer two types of Lead Reduction. Our granular activated carbon has a natural lead adsorption capacity about equal to its capacity for VOC Reduction, so products Certified for VOCs are usually Certified for Lead also. In addition, we have developed an additive for our MicroPure® precoat media mix which adsorbs lead, so precoat filters can now be Certified for Lead Reduction for their usual capacities.
4. Filter life is not specified for mechanical filtration claims because of the extreme variability of water supplies, but all other claims have gallonage figures. Standard 42 capacities include a 20% safety factor, but standard 53 requires either 100% extra or an accurate automatic alarm or shut-off.

This Technical Bulletin is courtesy of Pentair Everpure, Inc.