Thousand Oaks Water Hardness & Quality Report (2026)

The Thousand Oaks/Newbury Park Water System is operated by American Water, serving approximately 17,000 residences and businesses in Thousand Oaks and Newbury Park, Ventura County, California. The utility distributes up to 15 million gallons per day, sourced entirely from treated surface water purchased from the Calleguas Municipal Water District. Water originates from State Water Project allocations via the California Aqueduct, drawing from reservoirs including Castaic Lake and Pyramid Lake in the Sierra Nevada foothills, with local inputs from Lake Bard and connected impoundments. Treatment at Calleguas facilities includes coagulation, filtration, and chloramination before distribution.

Water travels through the Calleguas Creek Watershed, spanning the Transverse Ranges with influences from the Santa Susana Mountains. The geology features Franciscan Complex melange — chert, greywacke, and serpentine from Mesozoic subduction zone accretion — overlain by Pleistocene alluvium and Quaternary fan deposits. The limestone-bearing Vaqueros and Topanga Formations, alongside the Monterey Formation and Modelo Formation rich in limestone, dolomite, and evaporitic deposits, contribute dissolved minerals. These carbonate and volcanic rock types naturally dissolve calcium and magnesium ions during runoff, yielding a moderately hard supply.

Hard water promotes scale buildup in pipes, heaters, and fixtures, most affecting water heaters, dishwashers, washing machines, and coffee makers by reducing efficiency and lifespan. Soap scum forms readily, and spotting occurs on glassware and fixtures. Regular descaling with vinegar solutions, installing sediment pre-filters, and flushing water heaters annually helps mitigate effects. A water softener is recommended. Water pH averages 8.4; the system complies with lead and copper rules, and no PFAS detections above limits have been noted in recent reports.