By Shannon Murphy

There are a number of ways a manufacturer can get a product certified to an ANSI/NSF Drinking Water Treatment Unit (DWTU) Standard. Component manufacturers can get their products certified for material extraction and— in special cases like reverse osmosis (RO) membranes and bottled water applications —for reduction claims. (Bottled water applications are allowed a filter claim for removal of Cryptosporidium; but this is a special circumstance only available to bottled water applications.) These components can then be sold to system manufacturers as already meeting a portion of the requirements of the standard. System manufacturers can then use these certified components in their products, potentially reducing the cost and time in getting their products certified to the standard.

There are different guidelines for each type of certification.

Component certification
Manufacturers of carbon, carbon blocks, auxiliary faucets, RO membranes, etc., can submit products for certification. The component certification process is similar to that for system manufacturers. A submittal of a wetted parts list, exploded diagrams and formulation information on all wetted parts is required. An audit will be conducted, reviewing this information for accuracy. Samples of the product to be certified will be taken either out of in house stock or off the production line, to ensure the manufacturer is not making a product especially for NSF audit in order to pass the standard, then manufacturing a different product later.

If the component is seeking only material extraction certification, it will be tested to section 4 (Material Extraction) of the standard. If it is a pressure bearing part, it would also be tested to section 5 (design and construction).

Manufacturers of carbon, replacement filters and the like will have their products tested against the material extraction requirements of the standard. These types of products will be unable to make any type of reduction claims such as chlorine or lead. This is basically because in order to ensure how a filter will perform in reducing contaminants, you must have the unit it is going to be in, with flow rates, size specifications, etc.—otherwise there’s no certainty in the operation of the unit.

However, One of the benefits of material extraction standardization however, is that these products are authorized to bear a certification mark on product packaging and literature. Additionally, the product is now more valuable to potential clients wishing to have their systems certified to the standard. These manufacturers are assured that certified components, which have already met some of the requirements of the standard, will speed up the certification process for the entire system.

Flushing & conditioning
With any system certification, there are flushing and conditioning instructions recommended by the manufacturer prior to use by the consumer. These same instructions must be recognized in component certifications. Two main items need to be addressed with this issue.

First, component manufacturers must recognize and detail what a sufficient flushing time is for their product. For many components such as carbon systems, five minutes of flushing may be all that’s required in order to clear the component of fines and extractants that would cause the product to fail an extraction test. For other types of components like RO membranes, it may take over an hour of flushing to accomplish this. It’s important to know your product and the needs of your customers in order to know what a proper flushing time should be.

More than sum of parts 
Second, system manufacturers must make sure that if they use certified components in the system that the flushing requirements of the system aren’t shorter than what was used to certify the component. It could be that a certified component required 15 minutes of flushing in order to meet the requirements of the standard. If the system using that component is submitted with 10 minute flushing requirements, it could potentially fail due to the listed component.

System certification
Manufacturers of systems are able to get their products certified, and unlike component manufacturers, are able to make many different reduction claims. Different technologies have different capabilities in what they’re able to remove from the water. Many of the new systems are in fact hybrids of different filtration technologies such as an RO system with a carbon prefilter and postfilter. By making the system a hybrid, the product may potentially be able to remove a wider range of contaminants from the water.

Frequently, a system using a certified component claims it’s a certified system. This is not so. Simply using all certified materials or using a certified filter in a system does not mean the system meets the requirements of the standard. In order to claim a product is certified to any of the ANSI/NSF standards, it must go through the certification process itself. As with components, a wetted parts list, exploded diagrams, detailed formulation information on all water contact materials, an audit and all corresponding testing are required in order to claim certification. Unlike most components, systems also require all literature to be submitted for review and compliance to the standard.

It’s also not a given that by using certified materials in the construction of a system it will automatically meet material extraction requirements. For products like this, a review by an experienced toxicologist is the minimal requirement to ensure these components, when put together, don’t extract anything over the regulated levels. Additionally, this system must meet physical performance requirements of the standard such as cyclic pressure, hydrostatic pressure and hydrostatic burst.

Replacement filters
Another important issue is use of replacement cartridges in certified systems. Whenever a system is certified, it’s done so with a specific replacement filter or series of replacement filters. It’s required in the literature section of the standard to clearly display what replacement cartridges are meant for the system. This will appear on the data plate or performance data sheet (PDS) of the certified system. If there are multiple replacement cartridges for a system, the system’s data plate and PDS will specifically list what replacement cartridges are meant for the system. Keep in mind systems cannot claim different capacities based upon the replacement cartridge. The manufacturer must provide alternate model numbers if there are different capacity claims associated with the replacement cartridge.

A system using the incorrect replacement filter could be subject to a number of circumstances causing product failure. For example, the replacement element could be fractionally smaller than the recommended element; it may appear to fit correctly, but the slightest difference in length could cause “blow by,” where the water takes the path of least resistance, not going through the filter but between the filter and the housing. The reverse can be just as bad.

Replacement filters for bottled water applications are often submitted for certification. These are tested for material extraction and cyst reduction using microspheres. In these applications there’s a requirement in the Cryptosporidium test where the filter is exposed to a pressure pulse, a structural test where the unit gets a hammer of water pressure to test integrity. During this test the filter sometimes blows off the housing, causing a failure.

If a filter is longer than the housing is designed for, the filter could crack during installation. If this occurs, a significant percentage of the water would flow through the fracture untreated. Another example is the effect of flow rate. Many of the systems have flow regulators built directly in to them. If a system with a flow rate of one gallon per minute (gpm) uses a filter that has been tested at 0.5 gpm, the water isn’t going to be in contact with the filter long enough for the water to be correctly filtered.

If a certified system is installed using a replacement filter that’s not designed for that system—previously defined as not listed on the data plate or PDS—then the certification is lost and any claims to being certified are invalid. Look for the certification mark and see what replacement components are designed specifically for that system. If the system is using a replacement component not listed on the data plate or PDS, contact the manufacturer or the certification agency for clarification.

Replacement filters for bottled water applications are often submitted for certification. These are tested for material extraction and cyst reduction using microspheres. In these applications there’s a requirement in the Cryptosporidium test where the filter is exposed to a pressure pulse, a structural test where the unit gets a hammer of water pressure to test integrity. During this test the filter sometimes blows off the housing, causing a failure

Alternate housings
Additionally, manufacturers of components can’t get their product listed using a housing manufactured by a competitor, or using a housing of another company’s listed system with out written consent from that company. This is done for many reasons, but most importantly for trade infringement. If the housing manufacturer alters the design of the housing, the component manufacturer would have to be notified to ensure the system has the necessary changes to maintain certification. This type of arrangement, however, is rare.

It’s beneficial for both system and component manufacturers to get certified to ANSI/NSF DWTU standards. For system manufacturers, it shows their products are part of an elite group meeting the requirements of a national and internationally recognized standard. Component manufacturers can market their products to system manufacturers as already meeting the extraction requirements of the standard, saving system manufacturers time and money in the certification process.

When inspecting products with certification claims, make sure all the correct components are being used in the system. Any discrepancies in what’s on the data plate or PDS should be clarified with the manufacturer or certification body.

About the author
Shannon Murphy is operations manager of the Drinking Water Treatment Unit program at NSF International in Ann Arbor, Mich. His bachelor’s degree in biology is from Concordia University in Montreal, Canada, and his master’s degree from Wayne State University in Detroit is in biology with an emphasis on limnology. Murphy can be contacted at (800) 673-6275, (734) 769-0109 (fax) or email: [email protected]

If you have questions concerning this column, or if there’s a topic you would like addressed, please let us know. Contact “Water Matters” at: WC&P Magazine, 7522 N. La Cholla Blvd., Tucson, Ariz., 85741; (520) 323-6144, (520) 323-7412 (fax) or email: [email protected].


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