El Dorado Hills Water Hardness & Quality Report (2026)

El Dorado Hills, California, in El Dorado County — one of the fastest-growing exurban Sacramento communities, a major upscale foothill community east of Sacramento at the western Sierra Nevada foothills, home of Promontory Town Center and numerous Sacramento exurban tech and professional families, and a major Sierra foothills residential community known for its oak woodland and Gold Rush heritage (El Dorado County was named for the legendary El Dorado — the city of gold — reflecting the California Gold Rush of 1848–1855) — draws its municipal water supply from Folsom Lake via the El Dorado Irrigation District (EID). Water hardness in El Dorado Hills measures 187.5 mg/L — classified as hard.

El Dorado Hills' hard supply — harder than expected for an American River watershed community — reflects the EID foothills distribution infrastructure characteristics. Folsom Lake (on the American River — the Sierra Nevada Batholith granite and metamorphic belt watershed, moderately calcareous-poor) provides relatively soft source water. However, the EID distribution infrastructure in El Dorado Hills serves a newer western Sierra foothills community developed primarily in the 1980s–2000s on calcareous metasedimentary foothills Belt Series terrain (the El Dorado Hills Foothills metamorphic belt — the Sierra Nevada foothills calcareous-moderate phyllite and schist zone). The calcareous foothills geology and EID distribution produce the hard 187.5 mg/L.

At 187.5 mg/L, El Dorado Hills residents face regular hard water challenges. Monthly descaling with citric acid solution is standard maintenance. El Dorado Irrigation District consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.