By Rick Andrew
Certification of POU and POE equipment can take on many different forms, depending on the technology involved, the types of claims being made and the specifics of the product in question. There are always nuances associated with the certification, including the scope of testing involved, the product marking and the purpose of the certification. One of the considerations regarding POU and POE is component versus system certification. The NSF/ANSI Drinking Water Treatment Unit (DWTU) standards include requirements for both. These requirements are significantly different, so it is valuable to understand them. There are also different purposes and intents of component versus system certifications that are equally important to understand.
What is the difference between a component and a system?
Starting with first things first, it is beneficial to under- stand the difference between a component and a system. Basically, a component is a piece, part or material that could be used to build or construct a system. Typical components that might be certified include filter cartridges, filter housings, RO membrane elements, activated carbon, mineral tanks used in the construction of water softeners, control valves and ion exchange resin. A system is a complete product with all the parts, pieces and media necessary to be installed and to treat water. Examples include countertop filter systems, RO systems and water softeners.
There are some product types that could be either components or systems, depending on how they are used. The most obvious of these is disposable inline filters. These filters could be systems used to filter the water, without any additional parts or pieces. Or, they could be used as postfilters incorporated into POU RO systems. These products could be certified either as components or systems, depending on the manufacturer’s intended end market.
Component certifications under NSF/ ANSI DWTU Standards are intended to be for business-to-business (B2B) purposes. The intent is to create a marketplace of certified parts and pieces from which system manufacturers can shop and choose. These components are all evaluated for material safety through extraction testing, so system manufacturers can be assured that these components conform to the standard and won’t cause any issues with contaminant leaching. Additionally, pressure-bearing components (such as filter housings, mineral tanks and control valves) are evaluated for structural integrity according to the governing standard. Manufacturers selecting these components can be confident that they will not leach excessive contaminants or have structural issues.
In contrast to component certifications, system certifications under the standards are intended to be for business- to-consumer (B2C) purposes. The idea here is that complete treatment products are fully evaluated for material safety through extraction testing, structural integrity if connected to a pressurized water supply, contaminant reduction, applicable general requirements and for completeness and accuracy of their product literature. These certifications provide assurance regarding the whole package of concerns that consumers might have.
Contaminant reduction evaluation is one of the most important aspects of complete system certification. Testing is required to establish that the system is effective in treating the water as advertised by the manufacturer. All systems are required to have at least one contaminant reduction evaluation in order to conform to the governing DWTU standard. For example, water softener systems must be capable of effectively reducing hardness in the water in order to conform to NSF/ANSI 44. Figure 1 demonstrates the key types of evaluations applicable to components and systems.
Figure 2 shows graphically the extent of evaluation required under NSF/ANSI 44 for a water softener control valve versus a complete water softener system. The control valve, being a component, is evaluated for material safety and structural integrity, but not for any of the other various requirements of a complete water softener system. This makes sense when considering these requirements—it would be impossible to evaluate a control valve for softening capacity, because a control valve by itself cannot soften water.
Although it would be possible to test a control valve for pressure drop, the results would not be meaningful with respect to a complete water softener system. The pressure drop of the complete system would be greater than the control valve only because of the additional components in the system, especially the ion exchange resin. It would also be variable depending on the design and construction of the complete system, especially depending on bead size and bed depth of the ion exchange resin and any underbedding that might be included.
Despite the fact that the control valve has significantly fewer requirements than the complete system, certification of the control valve has real meaning and value—not necessarily for end users, but for manufacturers of complete systems who are sourcing quality components.
Certification bodies each have their own certification mark- ing requirements. These requirements include information specifying whether the certification is a component certification or a complete system certification. This is very important to understand. For example, some certifiers may prohibit certification marking directly on components of POU and POE systems to help prevent confusion, whereas others may not. In any case, any certification statements must be read carefully to prevent misunderstandings.
For example, there could be cases in which a non-certified water softener system is manufactured using a certified control valve or mineral tank. Some certifiers may allow the use of a certification mark directly on the component. Here, the casual observer might see a certification mark on the control valve or mineral tank and assume that the complete water softener is certified. This assumption would lead to overconfidence in the extent of certification and evaluation of that water softener system, as clearly described in Figure 2. A closer look at the certification mark, however, would reveal the word COMPONENT or a statement indicating a component certification, making it clear that the entire water softener system is not certified.
Different requirements for different end uses
When it comes to standards and certification requirements for products, end use is always a major consideration. For example, leaching or migration of contaminants into water is of utmost importance when it comes to products intended to be in contact with drinking water. Contaminant leaching, however, is not nearly as important for products that will be used in wastewater or geothermal heating applications. Similarly, certification of POU and POE components has a different purpose than certification of complete systems. Component certifications are intended to provide a marketplace for manufacturers sourcing quality suppliers and parts, whereas complete system certifications are intended to provide a thorough and complete evaluation to assure several aspects of quality for end users.
Because of these significant differences between component and system certifications, it is important to understand this important distinction and to be sure of the scope of certification when reviewing certified POU and POE products.
About the author
Rick Andrew is the General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. He has previously served as the Operations Manager and, prior to that, Technical Manager for the program. 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 Andrew@nsf.org.