By Rick Andrew

The NSF/ANSI Drinking Water Treatment Units (DWTU) Standards include requirements for both point-of-use (POU) and point-of-entry (POE) water treatment systems. However, other than water softeners under NSF/ANSI 44, most of the evaluation and certification work conducted by the various certification bodies has centered around POU systems.

There have not been nearly as many third-party certifications of POE systems as POU systems. Part of the reason for this is that more POU systems are manufactured and sold compared to POE systems. POU systems typically have lower price points and are often easier to install than POE systems. POU systems also specifically treat drinking water, as opposed to POE systems that treat water used for laundry, dishwashing, showering, etc. For some applications including treatment of drinking water, POU systems have more popularity. However, there are other reasons why most certification of drinking water treatment systems has focused around POU.

Challenges with Testing POE Systems
Chemical reduction testing under the NSF/ANSI DWTU Standards is conducted with an end point based on the manufacturer’s rated treatment capacity for aesthetic chemical contaminants, and beyond the rated capacity for health-related chemical con­taminants. For typical POU systems with rated capacities in the range of 100 gallons to 1,000 gallons, the chemical challenge through the test end point can be completed in a week or two on the laboratory test bench.

POE systems can have much, much higher rated treatment capacities compared to POU systems. And even with the higher flow rates typical of POE systems, these high treatment capacities can mean that tests require several weeks to several months on the test bench to reach the end point. In addition to the factor of the time required to reach the test end point, the volume of test water required can be enormous. Preparation of very large volumes of test water is time consuming and expensive for the laboratory, which means it is costly for the manufacturer as well. Ultimately, the length of time and cost of testing is a deterrent to manufacturers considering third-party certification of POE systems for chemical reduction.

The Need for Third-Party Certified POE Systems
There are some drinking water contaminants that are health concerns not only when ingested, but also when inhaled, or when in contact with skin, such as in a shower environment. One example that has recently had some focus is 1,2,3-Trichloropropane (1,2,3- TCP). In July of 2017, the State of California implemented a State Maximum Contaminant Level (MCL) for 1,2,3-TCP of 0.005 μg/L, or 5 parts per trillion (ppt).[1] Exposure to 1,2,3-TCP can occur through ingestion, and also through dermal (skin) contact, and inhalation.[2]

Because the exposure to 1,2,3-TCP is from inhalation and dermal contact, in addition to ingestion, it is preferable to treat water contaminated with 1,2,3-TCP being used for drinking and bathing, which points to a POE solution. And with this chemical contaminant being regulated by the State of California, there is a strong drive to have POE systems that are third-party certified for reduction of 1,2,3-TCP that can be relied upon with confidence by home­owners dealing with 1,2,3-TCP contamination.

Actions Taken by the NSF Joint Committee on Drinking Water Treatment Units
The issue of POE testing and certification, the associated challenges, and market needs was discussed at the October 2020 meeting of the NSF Joint Committee. Based on this discussion, the concept of laboratory testing of scaled-down versions of POE systems for contaminant reduction was embraced. Testing of scaled-down versions of POE systems can reduce the overall water consumption in the laboratory and reduce costs. In fact, three of the third-party certification bodies involved in the discussion indicated that they were already utilizing their own technically justified scale-up calculation procedures, which allows them to work with scaled-down versions of POE systems in their testing and certification programs.

The Committee created a task group charged with considering adopting a specific approach for evaluation of scaled-down POE systems for contaminant reduction into NSF/ANSI 53. The group considered the engineering dynamics of testing and scaling up, along with appropriate calculations. The group focused on clearly defining the chemical test requirements for POU versus POE devices in each subsection of Section 7 of NSF/ANSI 53. In order to provide as much clarity as possible, the task group also developed an informational annex providing examples of the scale-up process for units. Based on suggestions from the NSF Joint Committee, the task group also updated Sections 6.3 and 6.9 of NSF/ANSI 53, relating to flow control and pressure drop requirements for POE systems.

Outcomes of the Task Group’s Work
The new requirements developed by the task group clarify the test requirements for POU vs. POE systems in each relevant sub­section of Sections 6 and 7 of NSF/ANSI 53. An informational annex that includes examples of how to scale up units with granular media of all kinds and units with carbon blocks was created. Additional clarifications to the new requirements were created, based on feedback from the NSF Joint Committee, including:

  • Clarifying that POE systems are exempt from flow control requirements put in place for POU systems.
  • Adding backwashing to the full-scale and scale-up test procedures for POE systems where the full-size unit needs backwashing.
  • Allowing two ways to test POE systems for chemical reduction:
    » Using one full-size POE unit; or
    » Using two properly sized scaled-down units.
  • Expanding flow rate calculations and guidance in Informative Annex 7.

Next Steps and Implications
These new requirements were officially approved through a consensus ballot process by the NSF Joint Committee on April 18, 2022. The new requirements must now be approved by the NSF Council of Public Health Consultants (CPHC), an oversight body convened by NSF to ensure that all standards adopted through NSF Joint Committees are firmly grounded in protection of public health. Once the CPHC approves the new requirements, they will be officially adopted into NSF/ANSI 53.

The expected outcome is that these new requirements will reduce the cost and time to test POE systems for reduction of health effects from chemical contaminants, providing additional value to manufacturers, regulators, and end users addressing contamina­tion situations. This value is expected to be significant regarding contaminants that may have toxicological exposure routes in addition to ingestion, such as dermal and inhalation, where POE solutions can address these multiple exposure routes and provide optimal overall protection.


Andrew_Rick_mugAbout the author
Rick Andrew is NSF’s Director of Global Business 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: [email protected]


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