Degradation of Plastic Pipes in Building Plumbing Systems: Coupled Effects on Heavy Metal Transport and Water Chemistry

ABSTRACT Due to the potential occurrence of heavy metals in tap water, it is critical to examine their interactions with plastic potable water pipe surfaces, as these pipes may undergo physicochemical degradation induced by residual disinfectants over time. Thus, this study investigated the influence of plastic pipe degradation and water alkalinity on the release of Pb, Cu, and Zn from crosslinked polyethylene type A (PEX‐A) pipes after they underwent heavy metal accumulation experiments. For this purpose, an accelerated aging process was conducted by exposing pipes to a solution with a total chlorine concentration of 2500 mg L −1 at 70°C for 6 days. Disinfectant decay and organic leaching characteristics were examined for new and aged pipes in both cold and hot water. Surface chemistry analyses of pipes after accelerated degradation revealed the formation of oxidized carbon surface functional groups and etched‐like surface morphology. Aged pipes demonstrated higher heavy metal accumulation in the presence of alkalinity compared to conditions without alkalinity. Cu accumulation was found to be the most prominent, followed by Pb and Zn. The new PEX‐A pipes released more metals than aged PEX‐A pipes at pH 6.0. This pH was selected to assess the sensitivity of metal release to pH changes under more aggressive water chemistry. For hot water, both new and aged PEX‐A pipes exhibited a significant reduction in total chlorine residual concentration after 12 h, with aged pipes showing a faster chlorine decay rate. Hot water also promoted organic leaching from both new and aged pipes at pH 6.0.