Vallejo Water Hardness & Quality Report (2026)

The City of Vallejo Water Department operates the public water system serving Vallejo residents, unincorporated areas of Solano County, and select customers in American Canyon. Water is sourced from Lake Berryessa via the Putah South Canal and from Lake Oroville via the State Water Project's North Bay Aqueduct, treated at the 42-million-gallon-per-day Fleming Hill Water Treatment Plant. A secondary system supplies Green Valley, Old Cordelia, Jameson Canyon, Suisun Valley, Willotta Oaks, and Gordon Valley from Lake Berryessa, Lakes Frey, and Madigan; the utility blends sources as needed before conventional treatment and distribution.

The supply originates in the upper Putah Creek and Sacramento River watersheds, encompassing the Vaca Mountains and North Coast Ranges underlain by Franciscan Complex rocks and overlying Tertiary marine sediments, including diatomaceous earth and siliceous shales. Surface runoff from granitic Sierra Nevada headwaters mixes with these formations, and alluvial deposits in the Vallejo embayment contribute mineral dissolution through rock-water interaction, collectively shaping a characteristically hard supply reflective of regional lithology.

Hard water in Vallejo promotes scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and increasing detergent use as soap scum forms readily. Annual descaling of fixtures, installing sediment pre-filters, and flushing hot water systems are recommended maintenance steps. A water softener is advised for households with scale issues to extend appliance life and improve cleaning. Treatment at Fleming Hill includes coagulation, filtration, caustic soda for pH and alkalinity adjustment, fluoridation, and chlorination; lead levels are below 90th-percentile action thresholds and water meets all state and federal standards.