Chino Hills Water Hardness & Quality Report (2026)

The City of Chino Hills Public Works Department operates the local water utility, serving approximately 80,000 residents in San Bernardino County. Water sources include local groundwater from City-owned wells and those of the Monte Vista Water District (MVWD) and Chino Basin Desalter Authority (CDA), blended with imported surface water from the Metropolitan Water District (MWD) delivered via the Water Facilities Authority (WFA). Recycled water from the Inland Empire Utilities Agency (IEUA) supplements the supply. Distribution occurs through a pressurized network fed by transmission lines from these providers.

The supply originates in the Chino Groundwater Basin, spanning the Chino Valley with recharge from local rainfall, imported surface water, and spreading grounds. Geologically, the basin features Quaternary alluvial deposits — sands, gravels, silt, and clay deposited by ancient rivers draining the San Gabriel and San Bernardino Mountains — overlying fractured Tertiary sedimentary bedrock rich in limestone and evaporites. These layers dissolve calcium carbonate and magnesium as groundwater percolates through, yielding a hard supply with elevated mineral content; high TDS reaches 610 ppm, while surface imports from distant reservoirs provide some dilution.

Mineral deposits form scale in pipes, reducing flow efficiency, and leave spots on glassware and fixtures after drying. Hot water heaters, dishwashers, washing machines, and coffee makers suffer reduced lifespan and higher energy use from buildup; annual vinegar descaling is recommended. Soap lathers poorly, increasing detergent needs, and a water softener is recommended for affected households. Recent third-party analyses note contaminants including arsenic, chromium-6, nitrates, tetrachloroethylene, and disinfection byproducts exceeding health guidelines, though legal limits are met. Treatment involves blending, chlorination, and desalination at CDA facilities.