South San Francisco Water Hardness & Quality Report (2026)
Water Hardness
3 grains per gallon
Source
mixed
pH Level
7.3
neutral = 7.0
Lead
0.002 mg/L
✓ Below action level
TDS
113.6 mg/L
Est. Daily Cost
$0.14
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In South San Francisco, your appliances are currently losing 7% efficiency due to mineral buildup.
| Appliance | In South San Francisco | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 7.9 yrs | 8.5 yrs | -7% |
| Washing Machine | 11.7 yrs | 12 yrs | -3% |
| Water Heater | 13.5 yrs | 15 yrs | -10% |
Regional Water Comparison
How South San Francisco compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ South San Francisco, California | 52 mg/L | 3.5 ppt | 🟢 Soft | mixed |
| San Bruno, California | 162 mg/L | 6.8 ppt | 🟠 Hard | mixed |
| Millbrae, California | 126.5 mg/L | 5.7 ppt | 🟠 Hard | mixed |
| Visitacion Valley, California | 186 mg/L | 7.5 ppt | 🔴 Very Hard | mixed |
| Daly City, California | 79.5 mg/L | 4.3 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How South San Francisco compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ South San Francisco | 52 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes South San Francisco's Water Unique?
Local geology and source profile
South San Francisco, California, in northern San Mateo County adjacent to San Francisco International Airport — the 'Birthplace of Biotechnology' (site of Genentech's original research facilities) — draws its municipal water supply from the San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy Regional Water System via the California Water Service (Cal Water) San Francisco District or directly through SFPUC distribution, sourcing from Hetch Hetchy Reservoir on the Tuolumne River in Yosemite National Park, Sierra Nevada. Water hardness in South San Francisco measures 52 mg/L — classified as very soft.
South San Francisco's very soft supply reflects the Hetch Hetchy water system's exceptional geology. The Tuolumne River at Hetch Hetchy Reservoir in Yosemite National Park originates from the Cathedral Range and Clark Range of the central Sierra Nevada — draining one of the largest exposures of Cretaceous granodiorite and tonalite (the Yosemite Valley granitic suite — Half Dome Granodiorite, El Capitan Granite, and Cathedral Peak Granodiorite) on Earth. These massive, very slowly dissolving granitic rocks produce some of the softest natural water in California. The SFPUC Hetch Hetchy system delivers this pristine, very soft Yosemite water 167 miles to the Bay Area through the Hetch Hetchy Aqueduct.
With hardness at 52 mg/L, South San Francisco residents enjoy very soft water with minimal scale challenges. California Water Service and SFPUC consistently deliver water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy Regional Water System via the California Water Service (Cal Water) San Francisco District — the Hetch Hetchy Reservoir Tuolumne River Sierra Nevada granodiorite source; very soft supply at 52 mg/L in San Mateo County (northern San Mateo County near SFO).