Coronado Water Hardness & Quality Report (2026)

California American Water serves the Coronado system, covering Coronado, Imperial Beach, and portions of Chula Vista and San Diego in San Diego County, California (Public Water System ID: 3710001). The utility purchases 100% treated surface water from the City of San Diego, sourced via the San Diego County Water Authority from local reservoirs, the Colorado River (approximately 70% imported), and Northern California via the State Water Project. Treatment occurs at City of San Diego facilities including the Miramar and Otay Water Treatment Plants, with distribution maintained by California American Water.

The supply derives from the expansive Colorado River Watershed and San Diego regional basins, encompassing ancient granitic and metamorphic rocks of the Peninsular Ranges alongside alluvial and sedimentary deposits from the Colorado River Delta. Imported waters channel from the Sierra Nevada and Sacramento-San Joaquin Delta regions, where volcanic and granitic formations contribute to mineral profiles. Limestone and dolomite dissolution alongside evaporitic gypsum and calcareous sediments prevalent in the arid Southwest impart a hard supply character, with elevated dissolved solids moderated only slightly by reservoir sedimentation.

Very hard water at 230 mg/L promotes heavy scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. Boilers and coffee makers show rapid encrustation, increasing energy costs by up to 20–30%. Monthly vinegar descaling, scale-inhibiting filters, and annual pipe inspections are recommended; a water softener is strongly advised to prevent spotting on glassware and prolong equipment life. Lead measured at 1 µg/L (AL 15 µg/L) and copper at 0.71 mg/L (AL 1.3 mg/L) are both compliant; treatment includes coagulation, filtration, chloramine disinfection, and fluoridation.