Water conditioning for LCR compliance and control of metals release in San Francisco's water system

Abstract

The experience of the San Francisco Public Utilities Commission (SFPUC) demonstrates that maintaining high pH (target pH 9.4 for Hetch Hetchy water and pH 8.6 and 8.9 for other water supplies) is an appropriate corrosion control treatment to comply with the Lead and Copper Rule (LCR) and to control metals release in low-alkalinity water and is more effective than adjusting the Langelier saturation index or augmenting alkalinity. A survey of corrosion control treatment for utilities treating soft, low-alkalinity waters found that high pH has been successful in minimizing the release of lead and copper from plumbing. The combination of water quality and distribution system conditions at SFPUC is such that a switch from free to combined chlorine had no effect on lead and copper release and LCR compliance. The analysis presented here was originally developed as part of a project and compliance report to the California Department of Public Health to evaluate corrosion control treatment at SFPUC following systemwide chloramination and fluoridation. Additional historical information and more recent water quality data are provided to complement the analysis.