Chino Water Hardness & Quality Report (2026)

Chino, California, in western San Bernardino County in the Chino Valley — historically famous for its dairy farms and now a major Inland Empire suburb — draws its municipal water supply through the City of Chino Public Works Water Division, sourcing from the Chino Groundwater Basin (managed by the Chino Basin Watermaster) via local production wells, and from Inland Empire Utilities Agency (IEUA) imported water (MWD deliveries — State Water Project and Colorado River blend). Chino is a major participant in the Chino Groundwater Basin management area. Water hardness measures 102.5 mg/L — classified as moderately hard.

Chino's moderate hardness reflects the Chino Groundwater Basin's water chemistry in the western San Bernardino County zone. The Chino Basin is recharged primarily by the Santa Ana River and by MWD spreading along Prado Dam and the Chino Creek drainage — bringing a blend of San Bernardino Mountains runoff (San Bernardino Mountains granodiorite — calcium-poor) and MWD import water. The basin's large alluvial fan deposits, derived from the Transverse Ranges and San Gabriel Mountains, include some calcareous material from the Mountain Pass and Crafton Hills calcareous zones but are primarily siliceous granitic alluvium — keeping hardness moderate. The MWD blend contributes additional mineral content.

With hardness at 102.5 mg/L, Chino residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. Dishwashers produce clean glassware with moderate rinse-aid use. City of Chino Public Works and IEUA consistently deliver water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.