El Cerrito Water Hardness & Quality Report (2026)

El Cerrito, California, in Contra Costa County on the east shore of San Francisco Bay between Richmond and Berkeley — an East Bay hillside community known for its El Cerrito Plaza and proximity to the Berkeley Hills — receives its municipal water from East Bay Municipal Utility District (EBMUD), which draws primarily from the Mokelumne River in the central Sierra Nevada via a long aqueduct system to the East Bay. EBMUD stores and treats Mokelumne water before distributing to its East Bay service area, with some supplemental local groundwater from East Bay hills wells.

The moderately hard 182.5 mg/L hardness and TDS of 572.3 mg/L are notably elevated compared to typical EBMUD Mokelumne supply (~70–90 mg/L), suggesting a significant local groundwater contribution in El Cerrito's specific service zone. The Mokelumne River originates in the Eldorado and Amador counties Sierra Nevada — draining Cretaceous granodiorite and metamorphic amphibolite of the Sierra Nevada batholith with very low carbonate content. However, local Contra Costa and Alameda County groundwater wells in the East Bay hills tap Quaternary alluvial and Eocene-Oligocene marine sedimentary formations that carry higher mineral loads, substantially increasing hardness and TDS when blended with the soft Mokelumne River water.

At 182.5 mg/L, El Cerrito residents experience moderately hard water that is notably harder than neighboring East Bay communities fully on Mokelumne supply. Scale accumulates in kettles and coffee machines within weeks, the dishwasher benefits from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling of heating appliances is the appropriate schedule. The PFAS level of 7.3 ppt warrants a certified drinking water filter — El Cerrito's position near the industrial Richmond waterfront corridor and the San Pablo Bay shoreline contributes to elevated PFAS compared to inland East Bay communities.