Communications Hill Water Hardness & Quality Report (2026)

San Jose Water Company delivers drinking water to over 1 million residents in San Jose, California, including neighborhoods east of State Route 87 and south of Curtner Avenue. Their supply is a mix: about 40% comes from local groundwater wells within the Santa Clara Valley Groundwater Basin. Another 30% is purchased surface water from the Santa Clara Valley Water District (Valley Water), originating in Upper Coyote Creek reservoirs like Anderson Lake and Calero Lake. The remaining 30% is treated imported surface water, also managed by Valley Water through facilities such as the Penitencia Water Treatment Plant and Santa Teresa Water Treatment Plant. This water travels through an extensive pipeline network to reach consumers.

The mixed water supply for Communications Hill draws from the Vina Del Mar formation, part of the Santa Clara Valley Groundwater Basin. This basin is filled with Quaternary-age alluvial sediments—sands, gravels, and silts—that have washed down from the Franciscan Complex bedrock and Sierra Nevada sources. These sediments often contain fragments of minerals like limestone and dolomite, which readily dissolve in water. Additionally, surface water from the Coyote Creek watershed, flowing through the Diablo Range and its varied rock types, contributes to the supply. The combination of these mineral-rich groundwater sources and surface water inflows results in a water supply that is characteristically hard for the region.

Homeowners may notice scale buildup on appliances like dishwashers, washing machines, and water heaters within three to five years, and spotting on glassware is common. Faucet aerators and showerheads can become clogged relatively quickly, sometimes requiring annual cleaning with vinegar. To combat these effects and extend the lifespan of your appliances by an estimated 30-50%, installing a whole-home water softener is often recommended. Such a system can also improve how well soaps and detergents lather. San Jose Water maintains the water's pH between 7.5 and 8.5, and recent data shows lead and copper levels well below state action limits. Trace amounts of arsenic and nitrate are monitored and kept low, with no reported PFAS exceedances above health advisories.