Fontana Water Hardness & Quality Report (2026)

Fontana, California receives its water supply through the Fontana Water Company — a subsidiary of SouthWest Water Company — which blends imported State Water Project (SWP) water delivered from the Sacramento–San Joaquin Delta via the Inland Feeder pipeline and Silverwood Lake, with local groundwater pumped from the Chino Basin and adjacent alluvial formations beneath the western San Bernardino Valley in San Bernardino County. During dry years, SWP allocations are reduced and the groundwater component increases, causing seasonal hardness variation. The combined supply measures 123 mg/L — classified as moderately hard.

Fontana's moderate hardness is primarily driven by its Chino Basin groundwater component. The Chino Basin Watermaster manages the underlying unconfined alluvial aquifer, which is recharged by percolating Santa Ana River water, mountain-front recharge from the San Gabriel Mountains, and managed spreading operations. As infiltrating water moves through Quaternary fluvial sands and gravels derived from granitic and gneissic San Gabriel Mountain erosion, dissolved calcium and bicarbonate accumulate to moderate levels. Imported SWP water — softer than local groundwater — dilutes the blended supply, but the groundwater fraction consistently elevates overall hardness.

At 123 mg/L, Fontana residents notice moderate scale accumulation on faucet aerators, showerheads, and kettle interiors over time — periodic descaling every two to three months keeps fixtures in good condition. Dishwashers perform better with rinse-aid to prevent white mineral spots on glassware, and water heaters benefit from an annual inspection to clear lime deposits from heating elements. For households drawing higher proportions of Chino Basin groundwater during drought years, a whole-house scale inhibitor or under-sink RO system provides reliable hardness management and protects long-term appliance efficiency.