San Francisco County, California: drinking water report. San Francisco County comprises the city and county of San Francisco, a densely populated peninsula…
San Francisco County comprises the city and county of San Francisco, a densely populated peninsula surrounded by water on three sides. The San Francisco Public Utilities Commission delivers water to approximately 2.7 million people across the Bay Area, with 85% sourced from the Hetch Hetchy Reservoir in Yosemite National Park and the remainder from local reservoirs in Alameda and San Mateo counties. This regional system supplies neighborhoods from the Financial District and Mission Bay to the Sunset District and Presidio.
San Francisco's water quality reflects both the advantages of protected Sierra Nevada snowmelt and the challenges of aging urban infrastructure. The Hetch Hetchy system delivers naturally soft water that requires minimal treatment, though the city adds fluoride for dental health and chloramine for disinfection. The SFPUC consistently meets federal standards for drinking water contaminants, but residents face localized concerns related to the distribution system rather than source water quality.
Lead contamination represents the most significant documented risk in San Francisco households. The city contains an estimated 25,000 to 35,000 lead service lines connecting older properties to the water mains, concentrated in neighborhoods built before 1940. While the water leaving treatment plants contains no lead, it can leach from these aging pipes and household plumbing fixtures. The SFPUC has identified elevated lead levels in some homes, particularly those with full or partial lead service lines. Buildings constructed before 1986 also may contain lead solder in internal plumbing. The utility operates a lead service line replacement program, but thousands of connections remain.
PFAS (per- and polyfluoroalkyl substances) testing under EPA monitoring requirements has detected these synthetic chemicals at low levels in some Bay Area water systems. San Francisco's Hetch Hetchy source generally tests below detection limits for PFAS due to its remote, protected watershed. Local groundwater sources that supplement the system during dry periods show more variable results. California adopted some of the nation's strictest PFAS standards in 2024, and utilities across the state are installing treatment systems to meet these thresholds. Disinfection byproducts from chloramine treatment occur throughout the distribution system at levels below EPA limits, though some monitoring locations have measured total trihalomethanes and haloacetic acids in the upper range of acceptable concentrations.
If you live in a building constructed before 1986, particularly in neighborhoods like the Richmond, Sunset, or older parts of the Mission, test your tap water for lead or request information about your service line material from the SFPUC. Run cold water for 30 to 60 seconds before drinking if the tap has not been used for several hours, and never use hot tap water for cooking or drinking. Check your water to see current contamination data for your address, review our water filter guide for certified filtration options that address lead and other contaminants, and read the detailed report for comprehensive testing information. Visit the California state page for context on statewide water quality patterns and regulatory developments.