Los Gatos Water Hardness & Quality Report (2026)

San Jose Water Company supplies water to Los Gatos, California, in Santa Clara County, blending approximately 80% surface water from the Los Gatos Creek watershed with 20% from the Santa Clara Valley Water District (SCVWD). Key sources include surface water from the Santa Cruz Mountains via Los Gatos Creek, supplemented by SCVWD treated surface water and groundwater. Treatment occurs at facilities managed by San Jose Water and SCVWD, including filtration, chloramination for disinfection, and blending to optimize chemistry before distribution to the town and surrounding areas.

The Los Gatos Creek watershed spans the eastern Santa Cruz Mountains, draining into the Guadalupe River system within the Santa Clara Valley. This catchment features Franciscan Complex rocks — Jurassic–Cretaceous accreted terranes of volcanic and sedimentary origin including greywacke, chert, and serpentinite — that weather to release calcium and magnesium minerals into streams. Groundwater blended from SCVWD originates from the deep Santa Clara Valley basin aquifers, underlain by Quaternary alluvium and older Tertiary sedimentary formations such as the Santa Clara Formation, further contributing to the moderately hard character of the supply.

At moderately hard levels, Los Gatos water causes moderate scale buildup in dishwashers, washing machines, and water heaters, reducing efficiency and increasing energy use over time. Faucet aerators and showerheads may clog, and laundry and dish detergents perform less effectively, sometimes leaving spots. Monthly vinegar descaling, installing scale-inhibiting filters, or using high-efficiency detergents helps mitigate issues. A water softener is recommended for households with frequent buildup. Santa Clara Valley Water District water quality data confirms compliance with federal standards; treatment includes corrosion control for lead and copper rules, with PFAS presence monitored and some contaminants potentially exceeding EPA health guidelines.