Hard water in Phoenix, AZ
Reported by City of Phoenix Water Services Department · December 2025
- AZ typical
- 180 mg/L
- EPA health violations since 2016
- 1
- Softener for 3 people
- 24k grain
- Data
- Utility report
The water in Phoenix carries roughly 237 mg/L of dissolved calcium and magnesium, or 13.9 grains per gallon. That is very hard water. The number comes from City of Phoenix Water Services Department, dated December 2025.
At 237 mg/L, Phoenix is 57 mg/L above the typical Arizona figure of 180. None of the 10 nearest cities we track has harder water. The range nearby runs from 75 mg/L in Sun City to 208 in El Mirage.
What 237 mg/L means at home
Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.
Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.
Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.
Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.
What to do about it
At 237 mg/L most of the trouble is scale, and only a few things deal with it.
Ion-exchange water softener
The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.
Salt-free conditioner
No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.
Reverse osmosis or carbon filter
Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.
3 people × 75 gallons a day × 13.9 gpg = 3,118 grains a day. A 24,000-grain unit regenerates about every 7 days.
EPA record for Phoenix's water system
1 health-based violation since 2016
Serves about 1,695,000 people from surface water.
- Health-based
- 1
- Monitoring or reporting
- 3
- Open now
- 0
| Contaminant or rule | Violations | Period | Status |
|---|---|---|---|
| Surface Water Treatment Rulefiltration and disinfection | 1 | 2021 | Resolved |
Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.
Questions
Is Phoenix water hard?
Yes. It measures about 237 mg/L (13.9 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Phoenix in grains per gallon?
About 13.9 gpg. One grain per gallon equals 17.1 mg/L, so 237 mg/L divided by 17.1 gives 13.9.
What size water softener do I need in Phoenix?
For 3 people using 75 gallons each per day, 13.9 gpg works out to about 3,118 grains a day. A 24,000-grain softener covers that with a regeneration about every 7 days.
Has the Phoenix water system had EPA violations?
EPA records show 1 health-based violation for Phoenix City of since 2016, involving Surface Water Treatment Rule. There were also 3 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Glendale168 mg/LHard
- Paradise Valley171 mg/LHard
- Sun City75 mg/LModerately hard
- Youngtown75 mg/LModerately hard
- El Mirage208 mg/LVery hard
- Scottsdale172 mg/LHard
- Tempe180 mg/LHard
- Guadalupe172 mg/LHard
- Avondale105 mg/LModerately hard
- Chandler139 mg/LHard
Hardness data: TapWaterData US Water Hardness (utility report, December 31, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.