Twentynine Palms Water Hardness & Quality Report (2026)

Twentynine Palms, California, in San Bernardino County — a major Mojave Desert Marine Corps and Joshua Tree National Park gateway city (Twentynine Palms is a significant San Bernardino County city — the location of the Marine Corps Air Ground Combat Center Twentynine Palms (MCAGCC — the largest Marine Corps base in the United States by land area; the Combat Center covers approximately 932 square miles of Mojave Desert and is the primary large-scale combined arms training facility of the U.S. Marine Corps; MCAGCC is the dominant economic and demographic force in the Twentynine Palms area — the majority of Twentynine Palms's economy and population are directly or indirectly connected to the base)); Twentynine Palms is the main gateway community to Joshua Tree National Park (Joshua Tree National Park — one of the most iconic and distinctive national parks in the United States; the park straddles the Mojave and Sonoran deserts and contains extraordinary formations of Joshua Tree cacti, massive granite boulder formations, and spectacular desert landscapes; the main visitor center and northern entrance of Joshua Tree National Park is at Twentynine Palms; the park is one of the most popular parks in the national park system, attracting millions of visitors annually), a diverse San Bernardino County community with a primarily Marine Corps military, veteran, and desert community population — draws its municipal water supply via the Twentynine Palms Water District. Water hardness in Twentynine Palms measures 141 mg/L — classified as moderately hard.

Twentynine Palms's moderate hardness reflects the east San Bernardino County Mojave Desert basin's calcareous-moderate character. The Twentynine Palms Basin groundwater draws from Quaternary calcareous-moderate Mojave alluvium with effective treatment, producing the moderately hard 141 mg/L.

At 141 mg/L, Twentynine Palms residents encounter moderate scale accumulation. Monthly cleaning is recommended. Twentynine Palms Water District consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.