Eureka Water Hardness & Quality Report (2026)

The City of Eureka Water Department serves the city of Eureka in Humboldt County, California, providing drinking water to residents via the Eureka water system. Water sources include groundwater purchased from the Humboldt Bay Municipal Water District, supplemented by local wells tapping North Coast aquifers. Treatment occurs at conventional facilities using chlorine disinfection, with quality monitored at the City of Eureka Water Quality Laboratory (contact: 707-441-4363). The service area covers Eureka, CA 95501, with the department's mailing address at 531 K St.

The watershed encompasses the Humboldt Bay region, with groundwater sourced from coastal aquifers in sedimentary formations of the Eel River Basin. Key geology includes Quaternary alluvium and older Tertiary rocks like the Pismo and Monterey Formations, which contribute dissolved minerals. The Wildcat Group marine deposits and carbonate-bearing limestone layers dissolve calcium and magnesium as water percolates through during subsurface flow, resulting in a moderately hard, mineralised character without dependence on surface runoff.

At moderately hard levels, scale buildup affects water heaters, dishwashers, and laundry appliances most, reducing efficiency and lifespan. Faucet aerators and showerheads may clog, leading to lower flow rates. Maintenance tips include regular vinegar descaling, installing sediment filters, and flushing heaters biannually; a water softener is recommended to mitigate staining on fixtures and soap scum in bathrooms. Water quality meets all EPA health guidelines with no violations (Quality Score 100/100 per tapwaterdata.com); lead 90th percentile was 2.6 ppb in the 2024 CCR, well below the action level. The Unregulated Contaminants Monitoring Rule 5 (2024) found no detectable levels across 30 tested constituents, and treatment employs conventional filtration and chlorination.