January 2002: Volume 44, Number 1
Drinking Water System Components: Testing & Certifying
by Rob Herman and Blake Stark
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Testing and certification of drinking water system components fall under several ANSI/NSF Standards, depending on the product's final use. The component evaluation process, however, is basically the same with all standards. In addition to regulatory compliance, as required of most drinking water system components, there are additional benefits to component certification. Those assemblers seeking certification of drinking water treatment unit (DWTU) systems can find advantages in selecting components already certified to an existing standard.
The primary purpose of evaluating materials under the ANSI/NSF drinking water standards is ensuring materials that come into contact with drinking water don't impart levels of extractable contaminants exceeding the Maximum Drinking Water Levels (MDWLs) specified in the standards for regulated and unregulated contaminants. Consumers expect DWTUs will remove, and not add, contaminants from their water because of the unit's construction materials. Contaminants leaching from these materials may have critical adverse toxicological effects, including specific organs such as the liver, neurological and reproductive and/or developmental effects. Children may be especially sensitive to toxicological effects of certain contaminants such as neurological effects of lead exposure.
Formulation review process
Complete formulation information is required on any material not certified as specifically compliant with the sections of the U.S. Code of Federal Regulations, Title 21, Food and Drugs (Title 21 CFR) as listed in the standards. The standards only list wax and mineral oil lubricants, ion exchange resins, substances generally recognized as safe used in accordance with any conditions of the code, and solvents that may be considered for solvent bonding. Therefore, all housing materials, tubing, o-rings and gaskets, media other than specified ion exchange resins, storage containers, and other parts are required to be evaluated first by the material formulation review process.
Formulation information required includes the chemical identity of each ingredient in the material, its proportion by weight, supplier(s) of the ingredient, documentation regarding health effects concerns of each ingredient, and documentation regarding suitability of each ingredient for use in a potable water contact material. The ingredient and/or material supplier generally meets the latter two requirements using a Title 21 CFR citation or certification.
The formulation review is a key step in the evaluation of materials, and is instrumental in limiting the number of test failures. Therefore, materials incorporating the following ingredients, as well as numerous others, would be rejected at the formulation review stage and units incorporating them wouldn't be submitted for testing:
* Materials incorporating toxic heavy metal ingredients such as lead, cadmium or mercury pigments, lead stabilizers and arsenic antimicrobials,
* Pesticides other than chemicals evaluated as bacteriostatic agents,
* Regulated volatile organics for use as solvents in solvent cements,
* Substances prohibited under Title 21 CFR Part 189 from use as direct or indirect food additives,
* Recycled materials, and
* Automotive grade and other non-food grade materials.
A significant number of material formulations are already on file with certifiers. NSF has over 26,000 material formulations in-house (see Table 1).
Chemical extraction testing is generally done on the complete drinking water treatment unit or component to be certified. Occasionally, an individual material will be tested. This most often occurs if the material is an alternate for use in an already certified unit. Test results from both the material and unit are reviewed together to ensure the sum of detected levels of each parameter from the unit and material don't exceed the pass/fail level.
The unit or component to be tested is always installed, flushed and conditioned in accordance with manufacturer's instructions, and uses the exposure water specified in the appropriate standard. In the case of ANSI/NSF DWTU Standards, two sampling protocols have been used:
-- Prior to 1996, testing was done by filling the unit with exposure water (or immersing in the case of some components and most materials) and maintaining it for a 72-hour exposure period. A single sample was then collected for analysis.
-- Since January 1996, testing has been done by filling the unit with exposure water (or immersing in the case of some components and most materials) and maintaining it for 24 hours. A water sample is then collected. The unit is refilled with fresh exposure water (or re-immersed) and maintained for another 24 hours. A second water sample is then collected. The unit is again refilled with fresh exposure water (or re-immersed) and maintained for 24 hours. A third water sample is collected. The three samples are composited prior to analysis.
Details on the number of units to be used, and the amount of water collected for each sample, are presented in the standards. Units with absorptive or adsorptive media are tested with and without media. This ensures a fair representation of contaminants resulting from construction materials of which the unit may be made. Occasionally, testing to either the 72-hour static exposure or the three-exposure sequence of 24-hour exposures may be carried out three times to determine whether specific contaminants decline in concentration rapidly over time, and thus would be present for only a short percentage of the unit's lifetime.
Unit extraction testing may be waived if components -- when separately tested -- meet requirements of the appropriate standard and are assembled in a manner that doesn't introduce new components, increase the surface area-to-volume ratio of previously evaluated components, or which present potential concern based on cumulative factors.
The DWTU Standards include two pass/fail criteria. One is the MDWL and the second is an Advisory Concentration. Most tested contaminants have both criteria. The MDWL is generally a health-based level. Some health-based levels are very high, such as 1 milligram per liter (mg/L) for toluene and 10 mg/L for xylenes. Because consumers purchase DWTUs with the expectation these units remove contaminants from water, it's preferable DWTUs reduce contaminants well below the maximum health-based levels and don't add contaminants to the water. This lower level is referred to as the Advisory Concentration. The DWTU Standards require manufacturers to take all reasonable corrective action to reduce contaminants to below the Advisory Concentration. Note that the Advisory Concentration was formerly designated as good manufacturing practice (GMP) levels.
The standard specifies pass/fail criteria for regulated contaminants, aluminum, nickel, phenolics, total organic carbon, and carbon disulfide. These are routinely analyzed for all DWTUs. The MDWL is generally set at the USEPA or Health Canada regulatory level.
The standard also specifies pass/fail criteria for additional parameters required only when indicated by formulation review. They include screening parameters such as total dissolved solids and total Kjeldahl nitrogen; a few regulated contaminants; and unregulated contaminants frequently detected from materials commonly used in DWTUs. Most criteria are Advisory Concentrations based on significant toxicological concern (polynuclear aromatics and nitrosamines), or GMP (solvents).
It's interesting to note many products assembled using components with approved material formulations fail the material extraction test (see Table 2).
When an unregulated health effect chemical on neither table is detected -- whether it's a specifically requested chemical based on formulation review or a chemical specifically detected using a screening method such as gas chromatography with mass spectrometric detection -- an MDWL is required to be established in accordance with the procedures in ANSI/NSF Standard 61: Drinking Water System Components-Health Effects, Annex A.
Units and components are required to pass chemical extraction testing prior to certification. Materials tested individually are also required to pass chemical extraction testing before being used in a certified unit or component. Therefore, units and components with chemical extraction test failures shouldn't be available in the marketplace bearing a certification mark under the DWTU Standards. The unit or component, however, may be available in the marketplace without such a mark. Chemical extraction test failures represent potential risks to human health depending on the specific chemical and contaminant concentration in the drinking water.
Selection of components
If a component isn't certified to ANSI/NSF standards, then it's prudent for the assembler or manufacturer to check with the supplier to determine if the component formulation is on file with the certifier. Using components certified, or at least that have a formulation on file, will greatly expedite the certification process.
DWTUs are typically constructed using components from multiple vendors. The system assembler is relying on the component manufacturer to provide components meeting applicable standard requirements. The first selection criteria, at a minimum, will be those materials complying with Title 21 CFR or similar international standards. Meeting these requirements provides some level of assurance but isn't without risk. There remains the potential that the material -- based on final use application or manufacturing process -- can result in extraction test failure. These pitfalls can be avoided if components are already certified to one of the standards.
These components have been certified to the DWTU Standards and are evaluated for material extraction and -- when the component is pressure bearing -- structural integrity. Using a DWTU certified component will speed certification for system manufacturers by having formulation information and test data on file. Such information may exclude the system from further material safety (extraction) testing and/or structural integrity testing. This is especially useful if a product is already certified and manufacturers wish to use an alternate component.
ANSI/NSF Standard 14 is the standard for plastic pipe and related products. The components or products certified to this standard have the end use application noted directly on the product. These applications include potable water (pw); drain, waste, and vent (dwv); corrosive waste (cw); radiant (hydronic) heating (rh); reclaimed water (re); and sewer (sw). The intended end-use of the product determines the requirements necessary for certification. In most cases, this includes structural integrity testing, dimensioning, quality assurance requirements and marking.
For use in drinking water applications (i.e., pw), all Standard 14 products must also meet health effects requirements of Standard 61 to assure the product itself doesn't contribute contaminants to the water above the maximum allowable levels established in Standard 61. DWTU systems that use components evaluated and certified under Standard 14 for use with drinking water will speed up the process by having complete formulations on file and may allow structural integrity testing to be waived.
Drinking water additives
Drinking water treatment chemicals are evaluated to requirements of ANSI/NSF Standard 60: Drinking Water Treatment Chemicals-Health Effects. This standard sets criteria for evaluating health effects of these chemicals and addresses two principal questions. Is the chemical safe at its maximum use level? Are impurities below the maximum allowable levels? Examples of products covered under this standard include chemicals used in disinfection, coagulation/flocculation, pH adjustment, corrosion/scale control and fluoridation of drinking water. Products evaluated and certified to Standard 60 may be used in DWTU products if the use limitations aren't exceeded and the product continues to meet material safety requirements of the DWTU Standards.
Treatment & distribution
Drinking water system components used in municipal treatment and distribution are evaluated to Standard 61 requirements. The Drinking Water System Components-Health Effects portion of this standard evaluates components that come into contact with drinking water, with the exception of DWTUs. This standard sets criteria to determine which contaminants migrate or extract into drinking water, and whether the contaminant levels are below the maximum allowable levels in their intended application. Examples of products covered under this standard include pipes, coatings, gaskets, sealants, lubricants, pumps, valves, meters, faucets and drinking fountains.
Currently, there are efforts to harmonize requirements between Standard 61 and the DWTU Standards. A joint task group was formed from the DWTU and Drinking Water Additives Joint Committees to evaluate different protocols between the standards and develop protocols to determine material safety of components under all conditions. The task group has identified the media evaluation section of Standard 61 as the first section that needs to increase its scope to cover the typical use patterns of point-of-use/point-of-entry (POU/POE) components. Once complete, use of Standard 61 components in POE systems for certification under the DWTU Standards will be approved. This will increase the value of using Standard 61 components in DWTU products where material testing may not be required.
In all above cases, use of certified components will decrease time and cost in obtaining certification of drinking water treatment systems. If a certified component isn't available, ask the supplier if the formulation is already on file at your certifier since that will greatly expedite the certification process and minimize obstacles. If the component formulation isn't on file with the company's certifier, the evaluation of whether there are additive effects between the components cannot be made as required under Standard 53. Therefore, formulations must be on file with the company's certifier. This is one of the issues being addressed by the aforementioned task group.
About the authors
Rob Herman, technical manager of the DWTU program, has been employed at NSF for 16 years. He received a bachelor's degree in chemistry from Lawrence Technological University and a master's degree in environmental science from the University of Michigan.
Blake Stark is a key account manager with the NSF Water Distribution Systems program. Stark holds a bachelor's degree in geology from Adrian College and has worked at NSF for 12 years.
They can be reached at (800) 673-6275.