NSF Special Section-Oxidative Stability Requirements for PEX Pipe
In 2002, ASTM F876, Standard Specification for Cross-linked Polyethylene (PEX) Tubing, was updated to include a requirement for the oxidative stability in potable chlorinated water application. This was based on the test method F2023-03, Standard Test Method for Evaluating the Oxidative Resistance of Cross-linked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water.
The standard requires all PEX pipes used in potable water to be evaluated against the ASTM F2023 test method and have a minimum extrapolated test lifetime of 50 years at the end use conditions of 80 psi constant internal gauge pressure with water temperatures at:
NSF also offers a policy on the qualification of dependent transfer formulations for pipe, as well as minor formulation changes. The NSF Plastics Program Policies, Dependent Transfer Listing and Minor Formulation Changes, and Ingredient Changes-Colorants, Catalysts and Carrier Resins, are being used to test and evaluate PEX pipe according to the NSF P171 Protocol or ASTM F2023 test method. Under this policy, pipe manufacturers that use a PEX material listed to either ASTM F876 or NSF P171 for chlorine resistance can qualify for listing with a minimum amount of chlorine testing on their pipe.
These changes are a part of a growing trend in the plumbing industry to demonstrate that products can meet ever-increasing performance requirements. Recent changes have also been proposed (currently under ballot) to the ASTM F1281, F1282, F2262, F2389 standards through the ASTM (formerly American Society for Testing & Materials) Technical Committee that would require all composite PEX, composite PE and polypropylene pipes intended for use in potable water hot end-use applications to be tested and evaluated for oxidative stability.