Arizona Hard Water Levels by City (2025 Utility Data)
Most of the Phoenix metro has hard or very hard water. The minerals come from the rivers and aquifers the water passes through. Hardness isn't a health issue, but it causes scale in water heaters, fixtures, and pipes. Below are the numbers each utility published. Your exact level depends on your neighborhood and the water source that season.
How hardness is measured
| Hardness (mg/L as CaCO₃) | About gpg | USGS class |
|---|---|---|
| 0–60 | 0–3.5 | Soft |
| 61–120 | 3.6–7 | Moderately hard |
| 121–180 | 7.1–10.5 | Hard |
| over 180 | over 10.5 | Very hard |
To convert, divide mg/L (ppm) by 17.1 to get grains per gallon (gpg). Softeners are sized in gpg.
Hardness by city
| City | Published hardness | Source |
|---|---|---|
| Phoenix | 172–302 ppm (10–17.6 gpg) | Phoenix 2025 report |
| Scottsdale | 13–15 gpg south of Indian School Rd; 13–17 gpg north of it | Scottsdale 2025 report |
| Surprise (city water system) | Average 6.2 gpg, range 2.6–11.11 gpg (44–190 ppm) | Surprise 2025 report |
| Mesa | Varies widely by service zone. See the report | Mesa 2025 report |
Not all of Surprise is on city water. Some neighborhoods are served by private water companies such as EPCOR or Liberty, and their water can differ. Look at your bill to see who your provider is.
What these numbers mean for you
- Over about 7 gpg: you'll see white crust on fixtures and spots on glasses. A softener or scale-control system is worth considering.
- Over 10.5 gpg (very hard): scale builds up in water heaters and tankless units quickly. Flushing them regularly matters.
- A home test strip ([AFFILIATE LINK: Amazon-hardness-test-strips]) tells you what's actually coming out of your tap.
Next: How to choose a water softener for Phoenix water