Castaic Water Hardness & Quality Report (2026)

Castaic Lake Water Agency (CLWA) serves the Castaic community in northwestern Los Angeles County, California, providing drinking water to approximately 19,000 residents. Primary sources include Castaic Lake reservoir, imported State Water Project supplies from the Sierra Nevada via the California Aqueduct, and local groundwater from alluvial aquifers. Water is treated at facilities managed by CLWA and the Los Angeles Department of Water and Power (LADWP), ensuring compliance with state and federal standards as detailed in annual Consumer Confidence Reports.

The watershed spans the expansive California State Water Project system, originating in the Sierra Nevada, flowing through the Sacramento-San Joaquin Delta and Coastal Range before reaching Castaic Lake in the Santa Clara River Valley. Local geology features alluvial aquifers in unconsolidated Quaternary sediments overlying Tertiary bedrock, with contributions from fractured sedimentary rocks. These geological features — rich in dissolved calcium and magnesium — impart a very hard character to the supply, particularly from groundwater components.

Very hard water leads to significant scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. Faucets and fixtures develop stubborn deposits, and soap lathering is poor, increasing detergent use. Regular deliming of appliances and installing drain screens is advised; a water softener is highly recommended for households to mitigate these effects and protect plumbing. The 2023 CCR confirms compliance with all primary drinking water standards; tap water meets federal legal limits but has 2 contaminants above EPA health guidelines, prompting filter recommendations for vulnerable groups.