South Pasadena Water Hardness & Quality Report (2026)

The City of South Pasadena Municipal Water Department serves approximately 26,046 residents in South Pasadena, California, Los Angeles County. Water sources include local groundwater wells from the Main San Gabriel Groundwater Basin, imported surface water purchased from the Metropolitan Water District of Southern California — sourced from the Colorado River and Northern California via the State Water Project — and groundwater from Pasadena for the Pasadena Zone. Water undergoes monitoring, filtration, and disinfection with chloramines; the department is reachable at 626-403-7200, 1414 Mission Street, South Pasadena, CA 91030.

The supply blends local groundwater from the Main San Gabriel Groundwater Basin — formed from Quaternary alluvial sediments overlying the Tertiary Fernando Formation of siltstones and sandstones — with imported surface water from the Colorado River Aqueduct, which traverses Paleozoic and Mesozoic limestones and dolomites, and the State Water Project from Sierra Nevada granitic watersheds. Contact with carbonate-rich alluvial and bedrock formations imparts significant mineral content, producing a hard supply across all blended sources.

Very hard water promotes significant limescale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan. White deposits on fixtures and glassware are common, and soap lathering is inefficient, increasing detergent use. Regular vinegar descaling, sediment filters, and water heater flushing help mitigate effects; a water softener is highly recommended. The 2023 Water Quality Report confirms compliance with federal and state standards; lead and nitrate levels showed no exceedances; water is treated with chloramines and rigorously monitored across all sources.