Water hardness / San Diego
Is San Diego water hard?
Yes. San Diego tap water measures about 237 to 242 mg/L of hardness as calcium carbonate, which is very hard on the USGS scale. The City of San Diego Public Utilities Department does not publish total hardness; the figure is calculated from the calcium and magnesium averages it publishes for each treatment plant in its 2025 Additional Characteristics report (calcium hardness + 4.118 × magnesium).
about 237 to 242 mg/L very hard · 2025 Additional Characteristics report
What it means for curly hair
Calcium and magnesium from hard water settle on the hair. Lab work shows hair takes up a limited amount of these minerals, and damaged or bleached hair takes up more than healthy hair (Evans, Marsh and Wickett, 2011).
The evidence on breakage is mixed: two small studies found lower strength after repeated hard-water rinses (Luqman et al., 2016 and 2018), while an earlier one found no clear difference (Srinivasan et al., 2013). So hard water is a likely factor, not a proven cause.
What people commonly notice is curls that look dull, feel stiff or straw-like, and products that seem to work less than they used to.
What to do
- Use a chelating shampoo (look for disodium EDTA, tetrasodium EDTA or sodium phytate in the ingredients) about once a month as a starting point, and follow with conditioner.
- Change one thing at a time and judge it after two or three wash days, not after one.
- If your hair is bleached or color-treated, go slower: chelating can feel drying.
What not to do
- Do not clarify or chelate every wash: it strips more than minerals.
- Do not blame the water for sudden shedding, itching, flaking or scalp pain. That is a reason to see a dermatologist.
Check it yourself
The the City of San Diego Public Utilities Department report is public: 2025 Additional Characteristics 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.
Where the number comes from
Average calcium hardness and magnesium per plant: Alvarado 142 ppm and 23.1 ppm (about 237); Miramar 149 and 22.3 (about 241); Otay 136 and 25.8 (about 242). 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 2026-10-16. Rizzado did not measure this water.
Sources
- 2025 Additional Characteristics 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.
All cities · Phoenix · Las Vegas · Henderson · Los Angeles · Long Beach · Anaheim · Riverside · Houston · Dallas · Fort Worth
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. See how Rizzado works