Water hardness / San Francisco
Is San Francisco water hard? Somewhat.
Somewhat. San Francisco tap water measures 62 mg/L of hardness as calcium carbonate, which is on the line between soft and moderately hard on the USGS scale. The figure is the average the San Francisco Public Utilities Commission (SFPUC) publishes in its 2025 Water Quality Report. Up to 85 percent of the water comes from Hetch Hetchy and the rest from Bay Area reservoirs and a little groundwater, so the value at your tap can be anywhere in that range depending on the mix that reaches your neighborhood.
Where San Francisco sits on the scale.
San Francisco's published average is 62 mg/L. On the USGS scale, that is on the line between soft and moderately hard.
0–60Moderate
61–120Hard
121–180Very hard
180+
What it means for curly hair
At this level, mineral buildup is possible but usually slow. It matters more if your hair is bleached or damaged, because damaged hair takes up more calcium and magnesium (Evans, Marsh and Wickett, 2011).
Watch for the signs before changing your routine: curls that turn dull or stiff over a few weeks.
Hard water is a plausible factor, not a proven cause of breakage. Sudden shedding, itching, flaking or scalp pain needs a dermatologist, not a chelating routine.
Change less. Learn more.
What to try
No special routine follows from this number alone. If a consistent change appeared with a new water source, try one controlled comparison and keep the rest of your routine unchanged.
What to avoid
Do not turn one experiment into a fixed routine without a consistent reason to keep it.
Do not blame the water for sudden shedding, itching, flaking or scalp pain. That is a reason to see a dermatologist.
Every number keeps its source.
Non-regulated water quality parameters, Hardness (as CaCO3): range 8.1-112 ppm, average 62 ppm (2025 data). Classified with the US Geological Survey bands (soft 0 to 60, moderately hard 61 to 120, hard 121 to 180, very hard above 180 mg/L). Period: 2025. Checked against the source on 2026-10-17. Rizzado did not measure this water.
The the San Francisco Public Utilities Commission (SFPUC) report is public: 2025 Water Quality Report. Hardness can vary by area and season, and private wells or buildings with their own treatment can differ. If you want your exact value, ask the utility for your address.
Sources
- 2025 Water Quality Report
- Evans, A. O., Marsh, J. M., Wickett, R. R. (2011). The uptake of water hardness metals by human hair. Journal of Cosmetic Science, 62(4), 383-391.
- Luqman, M. W. et al. (2016). Effect of topical application of hard water in weakening of hair in men. Journal of the Pakistan Medical Association, 66(9), 1132-1136.
- Luqman, M. W. et al. (2018). To evaluate and compare changes in baseline strength of hairs after treating them with deionized water and hard water. International Journal of Trichology, 10(3), 113-117.
- Srinivasan, G., Srinivas, C. R., Mathew, A. C., Duraiswami, D. (2013). Effects of hard water on hair. International Journal of Trichology.
- U.S. Geological Survey. Hardness of water.
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Your water is one part of the picture.
Rizzado uses your city's water hardness, when there is a primary source, to adjust your routine. If your city is not here, it treats the value as unknown.
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