Mission District Water Hardness & Quality Report (2026)

The Mission District, San Francisco, California — San Francisco's iconic Latino cultural neighborhood, historically the cultural heart of San Francisco's Mexican-American and Central American communities, home of Dolores Park, vibrant Mission Street, iconic SF Mission murals, and increasingly gentrified tech worker community, centered on 24th Street and Valencia Street — receives its municipal water supply from the Hetch Hetchy Aqueduct (Tuolumne River–Yosemite watershed) via the San Francisco Public Utilities Commission (SFPUC). Water hardness in the Mission District measures 158.5 mg/L — classified as hard.

The Mission District's hard supply — substantially harder than Daly City (39 mg/L) using the same SFPUC source — reflects the southeast SF distribution zone's mineral accumulation pattern. The Hetch Hetchy Aqueduct source is extremely soft (approximately 30–50 mg/L — Yosemite Sierra Nevada Batholith granodiorite catchment). However, the Mission District distribution infrastructure includes some of the oldest SFPUC distribution mains in San Francisco (the Mission District was one of SF's first neighborhoods to be developed after the 1906 earthquake and fire, with water main infrastructure dating from 1907–1920s rebuilding). These century-old cast-iron mains accumulate substantial mineral content from the soft Hetch Hetchy supply, producing the hard 158.5 mg/L at Mission District taps.

At 158.5 mg/L, Mission District residents face hard water challenges — particularly notable given the very soft Hetch Hetchy source. Monthly descaling with citric acid solution is standard maintenance. SFPUC consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.