Fallbrook Water Hardness & Quality Report (2026)

Fallbrook Public Utility District (FPUD) serves approximately 25,000 residents in northern San Diego County, California, primarily the Fallbrook community (ZIP 92028). FPUD sources water from a mix of local groundwater via 24 production wells in the Fallbrook Valley Groundwater Basin and surface water imported through the San Diego County Water Authority from the Colorado River Aqueduct and State Water Project. Key facilities include the Raw Water Treatment Plant at Lake Henshaw (capacity 12 MGD) for surface water and multiple wellfields treated with filtration, chlorination, and fluoridation. Blending occurs at distribution points to meet demand peaking at 10 MGD.

The supply originates in the San Luis Rey River watershed upstream of Lake Henshaw and the local Fallbrook Valley Groundwater Basin. Geology features alluvial aquifers overlying Tertiary sedimentary rocks including the Pauba and Yucaipa formations, with limestone, dolomite, and volcanic deposits from Miocene to Quaternary periods. These carbonate-rich formations contribute dissolved minerals, yielding a very hard supply with elevated calcium and magnesium. Imported Colorado River water adds further mineralization from basin limestones, while local groundwater reflects prolonged contact with mineralized soils, shaping an overall hard character.

Very hard water promotes heavy limescale buildup in pipes, heaters, and fixtures, reducing water heater and dishwasher efficiency by up to 50% within 2–5 years. Most affected are tankless water heaters, coffee makers, washing machines, and irrigation systems, where deposits clog valves and nozzles. Maintenance includes annual vinegar descaling for appliances, magnetic descalers for pipes, and cartridge filters for faucets. A whole-house water softener is strongly recommended to extend appliance life and prevent spotting on dishes and glassware. FPUD maintains pH 7.5–8.5; lead/copper rule compliance is achieved with 90th percentile copper at 0.2 mg/L and no lead detections post-2016 pipe replacements. No PFAS exceedances are reported in the 2024 CCR; treatment involves coagulation/flocculation, multimedia filtration, and chloramination.