Rialto Water Hardness & Quality Report (2026)

Rialto Water Services (RWS), in partnership with the City of Rialto and Rialto Utility Authority (RUA), provides drinking water to approximately 110,000 residents across a 23-square-mile service area in San Bernardino County, California. The supply is entirely groundwater extracted from 22 production wells in the Chino Basin aquifer. Wellhead treatment facilities address specific contaminants, including perchlorate removal at two wells using ion exchange technology. Water undergoes site-specific filtration through sand, clay, rock, and gravel layers during extraction rather than centralized plant treatment.

The Chino Basin is a sub-basin of the Santa Ana River hydrologic region spanning San Bernardino and Riverside Counties, recharged via stormwater infiltration, spreading grounds, and imported State Water Project supplies. The basin features thick Quaternary alluvium from eroded Sierra Nevada and Peninsular Range materials, with aquifers in semi-confined sands and gravels overlying Pleistocene sedimentary formations influenced by limestone, dolomite, and evaporite-bearing rocks. These carbonate and mineral-rich strata dissolve calcium and magnesium ions during recharge, imparting a hard character to the supply.

Very hard water in Rialto causes significant scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan while increasing energy costs by up to 30%. Dry skin, soap scum, and spotted dishes are common household effects. Annual descaling of fixtures and appliances is essential, and a water softener is strongly recommended for homes. The 2024 Consumer Confidence Report shows no violations for lead or copper at the 90th percentile; perchlorate is fully addressed via wellhead treatment with zero detectable levels, and groundwater sources require less treatment than surface supplies.