Challenges Controlling Cuprosolvency in Drinking Water Using Minimum pH Criteria

Elevated cuprosolvency in drinking water can pose aesthetic and health concerns for residents and their pets. Gaps in the United States Environmental Protection Agency Lead and Copper Rule leave some consumers vulnerable to high-cuprosolvency water for the foreseeable future, creating a need for stakeholder guidance to address this concern. Initial work suggested that a bin approach or linear regressions could be used to identify a minimum pH target for given alkalinities to achieve acceptable cuprosolvency for nearly all waters. However, later work proved that these predictions were sometimes confounded by NOM, silica, and sulfate concentrations that affect pipe aging or concerns about calcite precipitation and aging time. Our research demonstrates that there are many exceptions to a minimum pH approach to controlling copper corrosion, at least as a simplistic function of alkalinity. We also demonstrate that some waters require interventions other than pH adjustment, such as the use of orthophosphate, to holistically address problems with cuprosolvency. Preliminary decision tree guidance was developed to reflect the complexity of the cuprosolvency problem.

Automated summary

Elevated cuprosolvency in drinking water poses aesthetic and health concerns. The Lead and Copper Rule in the United States has gaps, leaving some consumers vulnerable. Our research shows that a simple pH adjustment is not sufficient to address copper corrosion, and alternative interventions may be needed.