The NSF drinking water treatment unit testing and certification program includes standards to address the wide variety of point-of-use (POU) and point-of-entry (POE) drinking water treatment technologies on the market today, with more than 3,000 systems and 2,000 components currently certified under seven NSF/ANSI standards. These seven technology-specific standards are listed in Table 1.
The contaminant reduction claims that can be certified under the scope of each standard vary according to the capabilities of the different types of water treatment technology. Systems that utilize more than one treatment technology can be certified under multiple standards of the manufacturer’s choosing.
Drinking water treatment unit (DWTU) systems and components are certified based on the testing requirements shown in Table 2. A system is a complete product that is designed to treat residential potable water. Types of systems include plumbed-in, faucet-mount, point-of-entry, pour-through and shower filtration systems.
A component is defined as a part or subassembly of a system that must be combined with other components before providing the user with treated water. Some examples of certified components include filter cartridges, housings, reverse osmosis (RO) elements, faucets, filter media, fittings, tanks, tubing, valves and others. As with the certification of a complete system, component certifications help establish confidence in the safety and quality of the product, and the listings of certified components can serve as a buyer’s guide for system assemblers.
Material Safety Evaluation
All DWTU standards require both systems and components undergo a material safety evaluation composed of a formulation review and extraction testing. This process ensures that the materials in contact with drinking water do not leach levels of contaminants that exceed the maximum drinking water levels (MDWL) specified in the standards.
The starting point of the material safety evaluation is the wetted parts list (WPL) submitted to the certifying agency by the manufacturer. The WPL is a complete list of the product’s parts that come into contact with drinking water. From there, the certifying agency and the manufacturer work with suppliers to obtain the material formulations for each wetted part. Toxicologists then review the formulations for ingredients, monomers or impurities that could potentially leach into the water. This review is required by the standards and is a critical basis for the analytical scans established for the material extraction testing.
The material extraction testing begins by flushing the product in accordance with the manufacturer’s instructions and then filling or immersing the product in the exposure water outlined in the standard for 24 hours. A water sample is then collected. This procedure is repeated for two more 24-hour periods using fresh exposure water each time.
The three samples are composited and a full chemical analysis of the composited exposure water sample is conducted based on the formulary review of wetted materials. Any contaminant found in the water must not exceed maximum values, as indicated in each standard.
Structural Integrity Testing
In addition to the material safety evaluation, structural integrity testing is required for all plumbed-in systems and pressure-bearing components. Structural integrity testing is designed to simulate stress on the component over time. Depending on the type of pressure bearing component, the required structural tests can include cyclic pressure, hydrostatic pressure and burst pressure tests.
Each test is conducted using one new (previously untested) sample, such that the same sample does not have to survive a series of tests. Tests are not carried out to failure of the product, but rather to the end of the prescribed test where the product must remain intact and without any water leakage.
Contaminant Reduction Testing
Testing and certification of at least one contaminant reduction claim is required for all systems. After all, what would be the value of a DWTU system that did not reduce at least one contaminant from the water? A manufacturer may elect to certify multiple contaminant reduction claims based on the water treatment technology and claims available in the applicable standard(s). The contaminant reduction test procedures are provided in the standard and involve different water chemistries, as well as influent and effluent challenges based on the particular contaminant.
NSF offers optional contaminant reduction testing for those components that perform a treatment function. The tested component is not certified for the claims tested—certification of contaminant reduction claims is limited to complete systems because all parts together are needed to know the true system performance. However, many filter cartridge and media manufacturers are interested in providing independent, third-party test data to demonstrate the component’s contaminant reduction capabilities. The test methods follow those of the NSF/ANSI standards and a summary of the successfully completed performance testing appears in the component listing as a footnote, including tested flow rate, capacity and individual contaminants tested.
The process also includes a literature review of the proposed packaging, labels and manuals to verify conformance to all requirements in the applicable standard(s). Finally, annual inspections of the manufacturing facility and five-year retesting are conducted to ensure continued product compliance.
The DWTU standards are not static, archaic documents, but rather are continually updated by the Joint Committee on DWTUs to ensure they remain current with the latest scientific information and technology. For example, beginning in July 2007, all drinking water filtration systems certified for lead reduction must meet the new test requirements that were added to NSF/ANSI Standard 53. Lead contamination of drinking water can be the result of the presence of either particulate or soluble forms of lead. Both forms can cause a variety of adverse health effects in humans.
The previous lead reduction test protocol did not require challenge water with a specific percentage of particulate lead in addition to the soluble lead present. The new lead pH 8.5 method reliably generates a consistent percentage of particulate lead in the challenge water, thus ensuring that products certified for lead reduction are capable of treating both particulate and soluble lead.
The DWTU standards include thorough testing requirements and contaminant reduction claims that are aligned with various types of products and treatment technologies. Public health and safety in regards to these certified devices is consistently assured through a defined follow-up program as well as regular updates to the standard as new information and methods become available.