By Rick Andrew

The concept of a certified drinking water treatment unit (DWTU) system is not difficult to grasp. The system is a complete product designed to treat residential potable water. Manufacturers of these systems have operations spanning a wide range in terms of their level of vertical integration. Some are highly vertically integrated, combining internal molding, machining, carbon block making and system assembly operations. Others are less vertically integrated and may limit the scope of their operations to assembly of purchased components.

For these less vertically integrated operations, the selection of components is critical. The components must be available in the necessary quantities through a reliable source, acceptably priced and of acceptable quality in terms of material safety and (where applicable) structural integrity. Certain components, such as filter cartridges and reverse osmosis elements, must also be relied upon for contaminant-reduction performance.

This is where the concept of certified DWTU components fits in. By establishing material safety and, where it applies, the structural integrity of components, component manufacturers can create confidence for prospective customers that their components are appropriate for use in DWTU systems. For system manufacturers, certified components form the building blocks that can be relied upon for DWTU system construction.

Components conformance
A common question from component manufacturers is, “I’m confident in the material safety of my filter housing. Can I certify it for structural integrity only, to help prove its structural integrity to my customers?” Or, the question might be, “My company does a great deal of structural integrity quality control testing on our resin tanks. Would it be possible to certify them for material safety only, as our laboratory does not have the capability to perform that testing?”

The answer in both cases is no. The reason is that although the manufacturers have a high degree of certainty regarding the conformance of certain aspects of their products, a product certifier must have all the necessary independent certification test data in order to grant a certification. A prospective purchaser of a certified component would expect that the certifier has independently confirmed that the product conforms to all applicable requirements. The only way for the certifier to be absolutely sure is to test.

Systems requirements
Like components, pressure-bearing DWTU systems must conform to both material safety and structural integrity requirements of the standards. Additionally, they must be tested for and make at least one contaminant reduction claim. There is no reason for a DWTU system that does not reduce any contaminants. There is no maximum number of contaminant reduction claims, except for the limitations of the technology and the suite of claims established in the standards. There are some DWTU systems certified to reduce over 20 different contaminants.

Under Standards 42 and 53, there are no specific contaminant reduction claims that must be made. The one stipulation is that the only claim on a system cannot be bacteriostatic effects under Standard 42 (because that would be a filter that does not filter anything; simply a device that does not contribute to bacterial loading). Who would want a system that only claimed it did not contribute heterotrophic bacteria to the water?

Standard 58 requires that all RO systems must reduce the number of total dissolved solids (TDS). Standard 62 has a similar requirement for distillation systems. Water softeners must be tested for softening capacity and must meet minimum requirements for softening performance and rinse effectiveness. Ultraviolet systems must meet minimum UV dosage requirements for either Class A (40 mJ/cm2) or Class B (16 mJ/cm2) systems.

DWTU systems must also be tested to establish conformance to other minimum requirements, such as limitations on flow rates, that the filter media remain intact under pressure drop and limitations on pressure drop for point-of-entry systems. These minimum test requirements vary by standard and are specific to the technology being evaluated. Systems must also be sold with product literature that conforms to the requirements of the applicable standards. This literature includes a data plate that is permanently affixed to the system; a performance data sheet summarizing operating specifications, contaminant reduction performance and warranty information; an installation and operation manual that includes a variety of information; and where applicable replacement element packaging requirements to help consumers find the correct replacement element for their system. For a quick reference to requirements for certified components and systems, see Figures 1 and 2.

Contaminant reduction performance
Certain components, such as filter and RO elements, are designed with contaminant reduction capabilities in mind. However, their specific performance will depend on the system in which they are installed. For example, if a filter element does not seal properly in a system, that system will not perform. For filter elements containing media, flow rate through the system is critical, as it determines contact time with the media. If an RO element is installed in a system that has poor backpressure characteristics, that system will negatively impact the production rate and rejection performance of the element.
Nonetheless, it may be possible for a certifier to conduct contaminant reduction testing on these components to demonstrate their potential performance under specified operating conditions. Although this testing is not certified, it can help to generate sales because the testing is conducted by an independent laboratory. It may also be possible to structure a DWTU component testing protocol to allow the contaminant reduction testing to transfer to specific systems, if various applicable criteria are met. This may allow component manufacturers to help system manufacturers certify their systems at a lower cost. The ability to demonstrate contaminant reduction performance and to potentially lower certification costs for system manufacturers makes these data transfer scenarios invaluable marketing tools for component manufacturers.

Not a short cut
There is one scenario for which component certification is not intended—as a short cut to a certification mark. Because components are not tested and certified for contaminant reduction performance and for other system requirements, the cost to achieve certification is lower than for systems. This can tempt manufacturers to request certification of a component of their system, but not the system as a whole. They may believe that they can achieve greater acceptance by consumers and retailers by pointing to certification of their replacement element for material safety only.

However, this is not the intent of component certification. In this scenario, the component in question is not available on the open market for system assemblers. In fact, it is actually a replacement element for a non-certified system. The material safety, structural integrity, contaminant reduction performance and product literature of this system has not been evaluated for conformance to the applicable standards.

Certification policies of most certifiers require that certified components may not directly bear certification marking. These policies are designed to prevent situations such as the one described herein from being misleading to consumers and retailers.

Component certification
Without component certification, system assemblers would have little or no independent, third-party information to use as a basis for component selection. They would have difficulty determining which components would be appropriate for building certified systems. They might also experience unexpected certification test failures for material safety or structural integrity due to the selection of inappropriate components.

Having an array of certified components to choose from helps eliminate this confusion, expediting the certification process for system assemblers. For this reason, component certification is beneficial to assemblers, and because it benefits assemblers, it is a powerful marketing tool for component manufacturers. Like all DWTU certifications, component certifications help establish confidence in product safety – which in the end benefits us all.

About the author
Rick Andrew has been working with certification of residential drinking water products for NSF International for six years. He has been the technical manager of the Drinking Water Treatment Units Program for three years. His previous experience is in the area of analytical and environmental chemistry consulting. Andrew has a bachelor’s degree in chemistry and an MBA from the University of Michigan. He can be reached at 1-800-NSF-MARK or email:


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