Water hardness
Water hardness by city, with the source for every number
Hard water carries more calcium and magnesium. These pages list the hardness of the tap water in 6 cities, each figure taken from the utility's or the health authority's own report and linked to it. A city without a public primary source has no page: an unknown value stays unknown.
Cities
| City | Hardness | Class | Source |
|---|---|---|---|
| Phoenix | 172 to 302 mg/L | hard to very hard | the City of Phoenix Water Services Department |
| Buenos Aires (page in Spanish) | 60.8 mg/L | on the line between soft and moderately hard | AySA |
| Monterrey (page in Spanish) | 292.43 mg/L | very hard | Servicios de Agua y Drenaje de Monterrey (SADM) |
| Porto Alegre (page in Portuguese) | 27.3 mg/L | soft | DMAE (Departamento Municipal de Água e Esgotos) |
| São Bernardo do Campo (page in Portuguese) | 42 mg/L | soft | Sabesp |
| São José dos Campos (page in Portuguese) | 18 mg/L | soft | Sabesp |
How hardness is classified
In milligrams per litre of calcium carbonate (mg/L as CaCO3), using the US Geological Survey bands:
- Soft 0 to 60 mg/L
- Moderately hard 61 to 120 mg/L
- Hard 121 to 180 mg/L
- Very hard more than 180 mg/L
Why it matters for curly hair
In the lab, hair takes up a limited amount of calcium and magnesium, and damaged or bleached hair takes up more (Evans, Marsh and Wickett, 2011). Studies on breakage disagree. Treat hard water as a likely factor in dull, stiff curls, not as a proven cause.
Method
Each value is the one the source publishes, classified with the USGS bands. Rizzado does not measure water. When a source gives an average we use it; when it only gives results by treatment system we use the median; when it only gives a range we show the range. Hardness can change by neighbourhood and season.
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