Altadena Water Hardness & Quality Report (2026)

Altadena Water Company (also known as Lincoln Avenue Water Company), based at 564 West Harriet Street, Altadena, CA 91001, serves the Altadena area in Los Angeles County. The utility operates as a semi-desert water system, with approximately 45% of supply pumped from the Raymond groundwater basin and 55% purchased from external sources. The system is regulated by the California State Water Resources Control Board, Division of Drinking Water (DDW). No specific treatment plant names are detailed in available reports, but the system focuses on disinfection and monitoring to meet state requirements.

Altadena's water supply originates from the Raymond groundwater basin, which underlies the Los Angeles Basin and consists of Quaternary and Tertiary alluvial and sedimentary deposits. These geological formations are naturally rich in dissolved minerals, particularly calcium and magnesium carbonates and bicarbonates. The basin's hydrogeology produces a characteristically hard supply, typical of Southern California's semi-arid region where mineral-laden groundwater and imported surface water combine to create elevated mineral content.

At very hard levels, Altadena residents experience significant scale buildup on fixtures and appliances, reduced soap lathering, dry skin, and accelerated wear on water heaters and dishwashers. The utility reports that extreme hardness causes approximately $1,630 in annual damage to household systems. Water softening treatment is strongly recommended for most residential and commercial users to mitigate these effects and extend appliance lifespan. The system is monitored for over 50 compounds under state supervision; recent data indicates 7 contaminants exceed EPA health-based guidelines (MCLGs), with annual Consumer Confidence Reports (CCRs) documenting all test results and treatment processes.