Hard water in Tempe, AZ

Tap water hardness
180mg/L
10.5gpg
Hard

Reported by Tempe City of · June 2025

AZ typical
180 mg/L
EPA health violations since 2016
2
Softener for 3 people
24k grain
Data
Utility report

Tempe water measures 180 mg/L (10.5 gpg) of hardness, hard by USGS standards. The number comes from Tempe City of, dated June 2025.

Tempe on the hardness scale, with nearby cities
060120180240300360+AZ typical 180Sun Lakes: 103 mg/LSun Lakes 103Avondale: 105 mg/LAvondale 105Chandler: 139 mg/LChandler 139Gilbert: 168 mg/LGilbert 168Glendale: 168 mg/LGlendale 168Paradise Valley: 171 mg/LParadise Valley 171Guadalupe: 172 mg/LGuadalupe 172Scottsdale: 172 mg/LScottsdale 172Queen Creek: 178 mg/LQueen Creek 178Phoenix: 237 mg/LPhoenix 237Tempe 180mg/L as calcium carbonate060120180240300360+AZ 180Sun Lakes: 103 mg/LSun Lakes 103Chandler: 139 mg/LChandler 139Gilbert: 168 mg/LGilbert 168Paradise Valley: 171 mg/LParadise V. 171Guadalupe: 172 mg/LGuadalupe 172Phoenix: 237 mg/LPhoenix 237180 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Tempe sits close to the typical Arizona figure of 180 mg/L. Of the 10 nearest cities we track, 9 have softer water and 1 has harder. The range nearby runs from 103 mg/L in Sun Lakes to 237 in Phoenix.

What 180 mg/L means at home

Expect white crust on faucets and showerheads, plus spots on dishes that come out of the dishwasher.

Kettles collect scale quickly. Water heaters build up sediment at the bottom of the tank, which makes them work harder over time.

Soap and detergent need a little more to lather, and soap scum shows up in the tub.

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 180 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.

Softener size for Tempe

3 people × 75 gallons a day × 10.5 gpg = 2,369 grains a day. A 24,000-grain unit regenerates about every 10 days.

Size it for your household

EPA record for Tempe's water system

Tempe City of · PWSID AZ0407100

2 health-based violations since 2016

Serves about 165,000 people from surface water.

Health-based
2
Monitoring or reporting
12
Open now
0
20162017201820192020202120222023202420252026Surface Water Treatment Rule (LT2)Total trihalomethanes (TTHM)'16'18'20'22'24'26Surface Water Treatment Rule (LT2)Total trihalomethanes (TTHM)
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Surface Water Treatment Rule (LT2)filtration and disinfection12017Resolved
Total trihalomethanes (TTHM)a disinfection byproduct12017Resolved

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 Tempe water hard?

Yes. It measures about 180 mg/L (10.5 grains per gallon), which the USGS classes as hard.

What is the water hardness in Tempe in grains per gallon?

About 10.5 gpg. One grain per gallon equals 17.1 mg/L, so 180 mg/L divided by 17.1 gives 10.5.

What size water softener do I need in Tempe?

For 3 people using 75 gallons each per day, 10.5 gpg works out to about 2,369 grains a day. A 24,000-grain softener covers that with a regeneration about every 10 days.

Has the Tempe water system had EPA violations?

EPA records show 2 health-based violations for Tempe City of since 2016, involving Surface Water Treatment Rule (LT2), Total trihalomethanes (TTHM). There were also 12 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 42 cities in Arizona

Hardness data: TapWaterData US Water Hardness (utility report, June 17, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.