NSF 61-certified HDPE geomembranes

Q: Hi, we are looking for options for NSF 61-certified high-density polyethylene (HDPE) liners for installation in a potable water tank, 95th-percentile concentration of free chlorine in the tank is 1.2 ppm (1.2 mg/L). The current liner (60-mil [1.5-mm] textured HDPE, installed in 1999) is damaged and needs to be repaired or replaced. We are not sure if the existing liner is an NSF 61-certified HDPE geomembrane. What do you need to be NSF 61 certified?

A: Nice to hear from you. Thank you for your question on NSF 61 certification. The National Sanitation Foundation (NSF) is a nonprofit organization located in Ann Arbor, Mich., founded in 1944, whose goal is to create standards for safety and sanitation to promote public health. If you manufacture, sell or distribute water treatment or distribution products in North America for finished water, your products typically comply with NSF/ANSI 61-2020. It is a performance-based standard that evaluates the type and amounts of contaminants that leach from geomembranes into drinking water, rather than setting prescriptive limits on content within the materials themselves. The tests used for any given assessment vary from a basic cold-water test at different pH levels to the more challenging chemical certification.

Product manufacturers are required to disclose exact materials and suppliers used for each formulation. NSF reviews material formulations and determines appropriate analytical testing to perform for the assessment. Analytical testing is formulation dependent, and toxicology evaluation is performed to compare results to acceptable limits. A technical evaluation is performed to compare results to acceptable limits by a team of experts at NSF. Once all requirements are met:

1. Products are certified by NSF and entitled to bear the NSF mark.
2. NSF 61-certified HDPE geomembranes appear in NSF listings, which are available online at http://www.nsf.org/certified-products-systems.