Alhambra Water Hardness & Quality Report (2026)

Alhambra, California, a historic city in the west San Gabriel Valley of Los Angeles County, draws its municipal water supply through the City of Alhambra Public Works Water Division, sourcing from the Main San Gabriel Basin groundwater (pumped from the Main Basin alluvial aquifer under Main San Gabriel Watermaster adjudication) and from Metropolitan Water District (MWD) imported water as a supplemental source. Alhambra is near the western end of the San Gabriel Valley where the alluvial fan from the San Gabriel River spreads across Los Angeles County. Water hardness in Alhambra measures 65.5 mg/L — classified as moderately soft.

Alhambra's moderately soft supply reflects the Main San Gabriel Basin groundwater character in the west San Gabriel Valley zone — an area recharged heavily by the San Gabriel River spreading operations at Whittier Narrows and the San Gabriel River channel recharge. The San Gabriel River originates in the San Gabriel Mountains — draining the Precambrian San Gabriel Anorthosite (a famous calcium-rich igneous rock type) and the Cretaceous San Gabriel Granodiorite. While anorthosite does contain significant calcium (plagioclase-dominant rock), the rapid mountain drainage limits calcium dissolution to moderate levels. The spreading ground recharge near the valley floor, where the river water percolates rapidly through coarse San Gabriel alluvial fan gravel, maintains the moderately soft character of the West Basin groundwater.

With hardness at 65.5 mg/L, Alhambra residents experience minimal to moderate scale challenges. Faucet aerators and showerheads develop deposits slowly — bi-monthly cleaning with citric acid solution is sufficient. Dishwashers produce clean glassware. City of Alhambra Public Works and MWD consistently deliver water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.