Historical - PEX Water Pipe
This information reflects our best understanding of product composition in 2015.
PEX piping is made from polyethylene that has been crosslinked. Three major crosslinking methods are used and are designated by the type of PEX: PEX-a (peroxide), PEX-b (silane), and PEX-c (e-beam). Types a and b are most common and since there is...
PEX piping is made from polyethylene that has been crosslinked. Three major crosslinking methods are used and are designated by the type of PEX: PEX-a (peroxide), PEX-b (silane), and PEX-c (e-beam). Types a and b are most common and since there is more LCA data available for type a, that type will be highlighted in this CP. PEX piping is primarily used for radiant heating and domestic cold and hot water applications. PEX intended to transport of potable water must be evaluated and certified for this purpose. Applicable standards are ASTM F876, ASTM F877, and NSF/ANSI 14. Due to possible leachants from the pipe, there are special flushing requirements prior to use. Some studies indicate that pipe additives and degradation products may be found in water coming from the pipe over extended periods of time. These leachant materials include antioxidants (and degradants of antioxidants) that are added to PEX to protect it from oxidative degradation as well as degradation from chlorine and hypoclorous acid, often added to potable water to prevent microbial growth. There is indication of industry movement toward antioxidants with lower leachability such as sulfur containing phenolics and HALS (Uponor,Sahar) but it is unclear to what extent these changes have been implemented. Alternatively, more resistant inner layers can be used in piping, but this does not seem to be the case for standard PEX.
This is a historical Common Product. A more up to date version is available here: https://pharos.habitablefuture.org/common-products/2079059