By Rick Andrew

The NSF/ANSI Drinking Water Treatment Unit (DWTU) Standards include requirements for POU/POE systems. These requirements address various aspects of the products, including safety of materials in contact with drinking water, structural integrity, contaminant reduction performance and information for the end-user. Standards are continually updated through a consensus process by the NSF Joint Committee on Drinking Water Treatment Units. This committee holds a physical meeting at least once per year, and also conducts meetings via teleconference and utilizes an online workspace to move forward with development and adoption of new standards and updates to current standards to reflect new regulatory requirements, technological advances and other changes. The activities of this group are administered and funded by NSF, but that agency does not control the decisions made. Only one of the 33 members on the committee is an NSF representative. The committee includes equal representation from three stakeholder sectors: manufacturers, regulators and users. Consensus among these members from the stakeholder groups must be reached to create or change standards. There are two recent changes to these standards that product manufacturers should be aware of, as these changes could impact them in terms of product design and marketing of their POU/POE systems.

Elimination of the burst test requirement
For many years, the structural integrity requirements of the NSF/ANSI DWTU Standards included three tests:

  • 15-minute hydrostatic
  • Cyclic
  • Burst

The burst test was typically applied only to nonmetallic components and not to complete POU/POE systems. Complete POU/POE water treatment systems typically required only 15-minute hydrostatic and cyclic testing, and did not require burst testing. The Joint Committee considered this situation and ultimately concluded that because complete POU/POE systems did not require burst testing it would make sense to remove that requirement from components of these systems. With this in mind, in early 2012, the NSF/ANSI DWTU Standards were updated to reflect their decision to remove the burst test requirement.

Single-capacity claim
The Joint Committee also considered an issue related to capacity claims on active media filters.  For many years, NSF/ANSI 42, 53 and 58 required that only one capacity may be claimed on any given filter, even though the actual treatment capacity may vary by contaminant. In other words, if a filter could meet the requirements of NSF/ANSI 53 for lead reduction to a capacity of 1,000 liters, and that same filter could also meet the requirements for VOC reduction to a capacity of 500 liters, then the manufacturer could claim only a capacity of 500 liters when both claims of lead reduction and VOC reduction were made. What was unclear, however, was whether this single capacity requirement bridged across standards. For example, if the filter described above could meet the requirement under NSF/ANSI 42 for chlorine reduction to a capacity of 2,000 liters, could the manufacturer claim one capacity for chlorine reduction under NSF/ANSI 42 and a different capacity for the contaminant reduction claims under NSF/ANSI 53?

Many Joint Committee members have long held the view that only one capacity per filter was allowed even if different standards were involved, which stemmed from the original intent of this requirement: to avoid consumer confusion. Claims of different capacities for different contaminants could lead to consumers being confused about when to replace their filters, especially if they are not sure which contaminants might be present in their water. It also leads to complications with filter-change indicators (also known as performance indication devices or PIDs), which inform consumers when to change the filter, based on the volume of water that has been treated and the capacity of the filter. But in reality, the standards were not worded in a way to make this view clear.

After discussion and balloting among the committee through the consensus process, the clarification was made in 2012 that indeed only one capacity may be claimed on a given filter, regardless of the number of standards and/or contaminant-reduction claims involved. Further, this capacity must be the lowest capacity associated with any of the claims under any standard. In the example above, in order for the system to conform to NSF/ANSI 42 and 53 for capacity claims, the capacity of the filter must be represented as 500 liters when making the claims of chlorine reduction under NSF/ANSI 42 and lead and VOC reduction under NSF/ANSI 53. See Figure 1 for additional explanation.

Keeping up-to-date
It is important to recognize that product standards are ever evolving. For manufacturers, this is especially important if certifications are involved or other claims of conformance are being made. Many changes to the standards are relatively minor and don’t require much adjustment on the part of manufacturers, as they continue to make sure their products conform. Occasionally, however, there are more significant changes that do have an impact on product design or the way that claims are expressed to consumers. These changes must be carefully monitored and assessed in terms of potential impact to assure continued conformance.

Recognizing the importance of these standards, NSF allows observers to be present at all NSF Joint Committee meetings. The agency also allows for observers to subscribe and view most documents, ballots and activities of the NSF Joint Committees on NSF’s online standards website at Attendance at these meetings and following various issues online can be great tools to help keep up-to-date and avoid costly surprises late in the game.

About the author
Rick Andrew is NSF’s Director of Global Busi- ness Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email:


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