Concord Water Hardness & Quality Report (2026)

Concord, California, in Contra Costa County east of Oakland, receives its municipal water supply through the Contra Costa Water District (CCWD), drawing primarily from the Sacramento–San Joaquin Delta via the Contra Costa Canal and from Los Vaqueros Reservoir — a 160,000-acre-foot off-stream reservoir in eastern Contra Costa County that stores blended Delta and State Water Project water for drought reliability. Water is treated at CCWD's Bollman Water Treatment Plant in Concord before distribution to the city's residents. Water hardness measures 97 mg/L — classified as moderately soft.

Concord's moderately soft supply reflects the Sacramento River Delta source water's character and the Los Vaqueros Reservoir blending system. Sacramento River water at the Delta is primarily fed by Sierra Nevada granite and metamorphic batholith snowmelt (inherently soft), diluted and blended with San Joaquin River tributaries from the calcareous Diablo Range and Coast Ranges. CCWD's Los Vaqueros Reservoir blends multiple Delta sources and provides a consistent, treated supply. The finished hardness of 97 mg/L is somewhat higher than a pure Sierra Nevada supply but reflects the Delta's mixed character, including calcareous Coast Range tributary input and the Diablo Range Franciscan Complex serpentinite and calcareous sedimentary terrain surrounding the reservoir.

At 97 mg/L, Concord residents experience moderate scale accumulation in household use over time. Faucet aerators and showerheads develop deposits after several months — bi-monthly cleaning with citric acid solution is sufficient. Dishwashers produce clean glassware with moderate rinse-aid use. Hot water systems accumulate minimal scale. Contra Costa Water District consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.