Is PEX Pipe Safe for Drinking Water?

Plumbing codes accept it. A HUD Office of Policy Development and Research article says PEX is listed in all model codes, the International Plumbing Code, International Residential Code, Uniform Plumbing Code and National Standard Plumbing Code, as an acceptable product for domestic water piping. A 2006 PEX design guide posted on HUD USER, prepared by the NAHB Research Center for plastic pipe industry groups and HUD's Partnership for Advancing Technology in Housing, says PEX testing and certification must comply with NSF/ANSI Standard 61, whose primary focus is minimum health effect requirements for chemical contaminants and impurities indirectly imparted into drinking water from products used in potable water systems.

New pipes can leach chemicals. A 2014 study in Water Research, indexed in the EPA's HERO database, found eleven PEX related contaminants in a six-month-old plumbing system, one regulated, toluene, and several unregulated. Monitoring new PEX-a, PEX-b and PEX-c pipes with and without chlorine for 30 days, it found odor and total organic carbon decreased for all pipes, but odor remained above the EPA's secondary maximum contaminant level.

A 2021 study of PEX-a drinking water pipes over their first five years in a new office building in Rauma, Finland, found that migration of volatile organic compounds into the water decreased rapidly during the first months, while tert-butyl alcohol concentrations were high in the first months after use began. It found that longer stagnation increased the organic compounds able to migrate into the water, and the authors say that in normal use it is advisable to run water properly before drinking it.