Rubidoux Water Hardness & Quality Report (2026)

Rubidoux, California, an unincorporated community in western Riverside County — a major west Riverside County community (Rubidoux is a significant unincorporated Riverside County community between Riverside and Jurupa Valley — a densely populated west Riverside County working-class community), adjacent to Mount Rubidoux Park (a City of Riverside park on a prominent hill — Mount Rubidoux Park was historically the site of one of the oldest annual Easter Sunrise services in the United States, held continuously since 1909), a diverse Riverside County community with a significant Latino-American majority population, and part of the rapidly growing Inland Empire region — draws its municipal water supply from the Western Riverside County groundwater basin and MWD import via the Western Municipal Water District. Water hardness in Rubidoux measures 171 mg/L — classified as hard.

Rubidoux's hard supply reflects the west Riverside County Santa Ana River basin alluvial aquifer's calcareous-moderate geology and MWD Colorado River blend. The Western Riverside County groundwater basin at Rubidoux draws from: the Quaternary Santa Ana River alluvial aquifer (calcareous-moderate — partially recharged from MWD Colorado River import spreading); and the MWD Colorado River import (approximately 280–320 mg/L). WMWD distribution produces the hard 171 mg/L.

At 171 mg/L, Rubidoux residents face regular hard water challenges. Monthly descaling with citric acid solution is recommended. Western Municipal Water District consistently delivers water meeting all California State Water Board and EPA Safe Drinking Water Act requirements.