FALL 2017

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B Y J E R E M Y B R O W N C rosslinked polyethylene tubing has been one of the most commonly used materials for residential housing in the U.S. and Canada for over 20 years, and the use of PEX is increasing in residential and commercial construction for plumbing, hydronic heating and other applications. Claims have been made in the past that PEX tubing adds chemicals to drinking water, which may be harmful to human health. However, those claims have ignored the fact that it is mandatory for PEX tubing to be tested and certified to NSF/ANSI 61: Drinking Water System Components — Health Effects, which is a standard that helps to ensure the product will not contribute harmful levels of contaminants to drinking water. NSF/ANSI 61 contains a test procedure for evaluating the concentration of any chemical contaminant that a material may contribute to drinking water. It also requires a toxicological assessment of the daily dose of that contaminant that a person may safely consume with no adverse health effects. For example, a test that NSF International conducted showed that some newly installed PEX tubing may sometimes contribute 1 part per billion (1 ppb) of xylene to drinking water. One part per billion is equivalent to one drop of water in an Olympic-size swimming pool. However, NSF/ANSI 61 defines the safe threshold for the total allowable concentration , or TAC, of xylene in drinking water as 10 parts per million. That is 10,000 times higher than the 1 ppb occurrence level for xylene added by PEX tubing. So while claims that "PEX adds xylene to drinking water" may alarm some consumers, the scientific data shows that the levels of xylene added are 10,000 times below the safety threshold. The NSF/ANSI 61 standard is maintained by a committee with equal representation from regulators (such as the U.S. EPA, Health Canada and state drinking water officials), users (such as water purveyors, utilities and engineers) and product manufacturers. The ANSI standard development process ensures that the standard was developed and is maintained using an open consensus process with representation by all stakeholders. Anyone may attend the committee meetings or submit suggestions for improving the standard. PRODUCT TESTING The product testing process for PEX under NSF/ANSI 61 is quite rigorous. First, a formulation review is performed on the raw materials to determine what possible contaminants could leach into drinking water. This review determines what type of chemical extraction testing is necessary for the specific product. PEX tubing is tested by exposing the tubing to formulated exposure waters, and then analyzing the exposure waters for contaminants. In other words, testing is designed to measure if contaminants leach from the tubing into special water that is aggressively formulated for this purpose. Products are tested at the intended temperature use. For PEX, this is 140 F for domestic hot water systems or 180 F for commercial hot water systems. Tubing specimens are conditioned by exposure to the formulated waters for 17 days, with the water being changed on 12 of those days. The water collected from the final day, which encompasses a 16-hour exposure period, is then analyzed for contaminants. Any contaminants found must be below the total allowable concentration established for the contaminants, or the product fails the test. For contaminants regulated by the U.S. EPA or Health Canada, the TAC is equal to the regulated level. For non- regulated contaminants, NSF/ANSI 61 sets health-based pass/fail levels based on review of available toxicity data using the risk assessment procedures in Annex A of the standard. Water exposed to PEX tubing and associated fitting systems is tested for the following contaminants as required by NSF/ANSI 61: > Volatile organic compounds > Semi-volatile compounds (base neutral acid scan by gas chromatog- raphy/mass spectroscopy) > Phenolics > Metals > Methanol > Tertiary butyl alcohol > Methyl tertiary butyl ether > Ethyl tertiary butyl ether > Any other potential contaminant identified during the formulation review These test methods are capable of detecting contaminants in water below 1 part per billion, and even lower for some contaminants. DETERMINATION OF TOTAL ALLOWABLE CONCENTRATIONS In addition to the approval by the standard committee, the TAC values go through external peer review by NSF International's Health Advisory Board. This panel consists of toxicolo- gists from the U.S. EPA, state regulatory agencies, Health Canada, academia, consultants and chemical manufactur- ers. The TAC values are then balloted by the NSF International Council of Public Health Consultants, which includes public health officials from the U.S. and Canadian federal, state and provincial governments. CONTINUOUS VERIFICATION OF PRODUCT SAFETY For PEX tubing listed for potable water applications, NSF International performs at least three unannounced audits of each production facility an- nually. During these inspections, it is verified that there are no modifications to the product formulation or process- ing. In addition, it is confirmed that quality control tests are being done by the manufacturer. The organization also collects samples for laboratory retesting of each product family on an annual basis. FINDING PRODUCTS THAT MEET REQUIREMENTS PEX tubing that meets the health effects requirements of NSF/ANSI 61 will bear either the "NSF-61" mark or the "NSFpw" (potable water) mark on the print string, and will be listed on nsf.org. The "NSFpw" mark indicates the product meets the health requirements of NSF/ANSI 61, as well as performance, long-term strength and quality control requirements as specified by NSF/ANSI 14: Plastic Piping Components and Related Materials. This provides assurance that drinking water coming from PEX tubing that is certified to NSF/ANSI 61 is safe for human consumption. Currently, 140 PEX tubing products (made by 27 companies) are certified for potable water applications in NSF International's certified product listings. Jeremy Brown, senior technical reviewer, has been with NSF International for 22 years and evaluates products for certifi cation to NSF/ ANSI 61 and NSF/ANSI 14. He serves on the Uniform Plumbing Code Technical Commit- tee and is a member of Southeast Michigan Code Study and Development and the Eastern Michigan chapter of the American Society of Plumbing Engineers. An overview of testing, certification of PEX plumbing BEHIND THE SCENES JASON KOLENDA/DREAMSTIME HVACPproducts.com HVAC & Plumbing Product News \ Fall 2017 16

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