Phoenix, AZ water hardness: 172–302 mg/L (10–17.6 grains per gallon)
The City of Phoenix Water Services Department reports total hardness of 172 to 302 ppm in its 2025 Water Quality Report. Most of that range is very hard on the USGS scale. The low end is hard.
The numbers as Phoenix states them
| Measure | Units (as printed) | 2025 range |
|---|---|---|
| Total hardness | ppm (mg/L) | 172–302 |
| Total hardness | grains/gallon | 10–17.6 |
| Alkalinity | ppm | 121–167 |
| Total dissolved solids | ppm | 464–716 |
Where the water comes from
The report says about 97–99 percent of Phoenix's 2025 water was surface water from the Salt, Verde and Colorado rivers. The rest (about 2 percent) came from about 20 city wells. Salt and Verde water arrives through the Salt River Project (SRP) canals. Colorado River water arrives through the Central Arizona Project (CAP) aqueduct, partly stored in Lake Pleasant.
| Treatment plant | Water it treats | Capacity |
|---|---|---|
| 24th Street | Salt River Project (Salt and Verde rivers) | 140 MGD |
| Deer Valley | Salt River Project | 100 MGD |
| Val Vista (shared with Mesa) | Salt River Project | 130 MGD |
| Union Hills | Colorado River (CAP) | 160 MGD |
| Lake Pleasant | Colorado River (CAP) | 80 MGD |
Hardness by plant or neighborhood: not published. We did not find a Phoenix document that gives hardness per plant or per area. Phoenix's Water Services FAQ says it blends CAP and SRP water. Your tap can sit anywhere in the 172–302 range, and it can change with the season and the blend. We will not guess a number for your neighborhood.
What 172–302 mg/L means at home
Water softener
Phoenix's range is 10–17.6 gpg. If you do not test, program the softener near the top of the range, about 18 gpg. A setting that is too low lets hard water through before the next regeneration. A setting that is too high only uses more salt and water. A test strip at your tap lets you set it closer. Phoenix's FAQ says softeners are a personal choice, not needed for safety, and asks owners to follow the maker's maintenance instructions.
Dishwasher
Use one of the highest hardness levels in the manual's table (10–18 gpg is about 10–17 °dH). Keep rinse aid filled. If your model has a salt reservoir, keep it filled too.
Kettles, coffee makers and water heaters
The report notes that hard water “can cause some types of scaling in pipes and water heaters, and on plumbing fixtures such as faucets and showerheads.” Plan on regular descaling of kettles and coffee makers, and on cleaning aerators and showerheads.
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Not on Phoenix water?
Scottsdale, Tempe, Mesa, Glendale, Chandler and other Valley cities run their own utilities and publish their own reports. Phoenix's former Anthem and Hedgepeth Hills systems are now served by the main Phoenix system, per the reports page.
Sources
- City of Phoenix, 2025 Water Quality Report (PDF), page 4: https://www.phoenix.gov/content/dam/phoenix/waterservicessite/documents/wsdprimarywqr.pdf
- City of Phoenix, Water Quality Reports page (all years): https://www.phoenix.gov/administration/departments/waterservices/water-quality/water-quality-reports.html
- City of Phoenix, Our Infrastructure (plants and source water): https://www.phoenix.gov/administration/departments/waterservices/development-infrastructure/our-infrastructure.html
- City of Phoenix, Tap Water Taste, Odor & Hardness FAQs (PDF): https://www.phoenix.gov/content/dam/phoenix/waterservicessite/documents/taste_odor_and_hardness_faqs_ENGLISH.pdf
- City of Phoenix, Water Services FAQs (CAP/SRP blending): https://www.phoenix.gov/administration/departments/waterservices/faq.html
- USGS Water Science School, Hardness of Water: https://www.usgs.gov/water-science-school/science/hardness-water