How hard is water in Phoenix, Mesa, Chandler and Tempe?

Hardness is the amount of dissolved calcium and magnesium in the water. Utilities report it two ways, and you will see both.

• Milligrams per liter (mg/L) or parts per million (ppm). These mean the same thing for our purposes.
• Grains per gallon (gpg). This is the unit water softeners and many dishwashers ask for. One grain per gallon equals 17.1 mg/L, so you divide mg/L by 17.1 to convert. Tempe's water utility gives that exact formula to residents who ask, and Mesa's report defines a grain the same way.

The USGS uses mg/L to rate water. Zero to 60 is soft, 61 to 120 is moderately hard, 121 to 180 is hard, and anything over 180 is very hard. Convert that cutoff and "very hard" starts at about 10.5 grains per gallon. Almost every reading in the Valley sits right at that line or above it.

Hardness is not a health issue. Phoenix's own report calls taste, odor and hardness harmless aesthetic aspects that some people notice. Tempe says the same thing another way: neither a primary nor a secondary federal standard exists for hardness. What hardness does is leave scale behind, and that is the reason people ask about it.

### Phoenix

Phoenix's 2025 report lists total hardness at 172 to 302 mg/L, which the city also prints as 10 to 17.6 grains per gallon. That is a wide range, because the city blends several sources. In 2025 about 97 to 99 percent of Phoenix's water came from surface water, mostly the Salt, Verde and Colorado rivers, and the rest came from about 20 city groundwater wells. Salt and Verde water arrives through the Salt River Project canals. Colorado River water arrives through the Central Arizona Project aqueduct.

So what should you plug into a softener? The report gives a range, not a single figure for each neighborhood, which means a number in the middle of the range is a starting point. If you want to dial it in, a home hardness test strip or a lab test at your own tap shows what your house actually receives. We cover Phoenix's numbers in more depth on our page about how hard Phoenix water is.

Phoenix also explains where the minerals come from. They leach out of the soils the source water crosses on its way to the treatment plants. Its report says hard water can cause some types of scaling in pipes and water heaters, and on faucets and showerheads.

### Mesa, by zone

Mesa is the clearest example of hardness changing inside one city. Its 2025 report divides the city into three zones based on where the surface water comes from.

• City Zone: Salt and Verde River water delivered through the Salt River Project, treated at the Val Vista plant. The report says this zone averages about 12 grains per gallon.
• Eastern and Southern zones: Colorado River water delivered through the Central Arizona Project, treated at the Brown Road and Signal Butte plants. The report says these zones average about 16 grains per gallon.

Mesa's report also warns that every zone can receive groundwater or a blend at different times of the year. The regulated contaminant table shows a very wide hardness range across samples, and the city explains why: depending on utility operations, the water you drink may include a higher share of groundwater, and its wells vary in mineral content.

The city gives one practical instruction. It recommends setting a water softener at 16 grains per gallon and then adjusting the setting to suit your needs and preference. It also points residents to a zone map in the report so you can see which zone your address falls in.

Here is what that means in mg/L. Twelve grains per gallon is about 205 mg/L and 16 is about 274 mg/L. Both are past the USGS "very hard" line of 180 mg/L. The zone difference is real, but neither side of it is soft water.

### Chandler

The City of Chandler's water quality FAQ says hardness in its drinking water ranges from a low of 5 grains per gallon to a high of 20, and the citywide average is 16.5 grains per gallon.

That range is the story. A reading of 5 grains per gallon is about 85 mg/L, which the USGS calls moderately hard. A reading of 20 is about 342 mg/L, nearly twice the "very hard" cutoff. The average of 16.5 falls in the very hard band. Which end you live near depends on the blend of supply your street receives at that moment.

If you own a softener in Chandler, the citywide average is a reasonable place to start. If your dishes spot heavily or your shower glass scales fast, test your own tap. A tap that reads at the high end would justify a higher setting.

### Tempe

Tempe does not publish one fixed number in its resident FAQ. It explains what moves it. Tempe's treatment plants get surface water from the Salt River Project and the Central Arizona Project. The mix changes with the seasons and from year to year, depending on precipitation and the annual runoff from snowmelt in the mountains.

Two facts from the city help you predict the direction. The Salt River water is characteristically higher in total dissolved solids and chlorides, while the Verde River water is higher in hardness compounds. So a year and a season heavy on Verde water tends to push hardness up. Tempe tells customers who need a number for a dishwasher or softener to check its latest Water Quality Report and to convert mg/L to grains per gallon by dividing by 17.1.

### Scottsdale, Gilbert, Glendale and the rest of the Valley

Those cities publish their own annual water quality reports, and their numbers depend on their own mix of Salt, Verde, Colorado and groundwater supply. We are not printing a hardness figure for them here because we have not confirmed one from each city's current report. Look for the line labeled total hardness in your city's latest annual report. If the report gives mg/L, divide by 17.1. If it gives grains per gallon, you are done.

The pattern still holds. If your water comes from the same rivers and canals as the cities above, expect hard to very hard water, and expect it to be at the harder end whenever your supply leans on groundwater or Colorado River water.

Hardness is the reason the same minerals show up as white crust on faucets, cloudy spots on glass and a chalky film in the shower. Heat makes the effect stronger, because minerals come out of the water faster as it warms. That is why scale collects on water heater elements and tank bottoms, and why tankless units need periodic descaling.

Here is where the number puts you to work.

1. 1Softener setting. A softener asks for your hardness in grains per gallon. Use your city's figure or your own test result. Mesa's own guidance is to start at 16 and adjust.
2. 2Dishwasher and detergent. Many dishwashers have a hardness dial. Use the same number.
3. 3Water heater care. Harder water means faster sediment. Our page on how often to flush a water heater in Phoenix explains the schedule.
4. 4Deciding on treatment. Our guide to how hard water damages plumbing covers what scale does to pipes and fixtures. If you are weighing a softener against a salt-free system, read whether salt-free softeners work.

Two more things to know. The number can drift year to year, so use the newest report. And a city average tells you about the water leaving the utility's system, not about your house. If your home has a softener already, or if a filter sits upstream of your tap, a test at the tap shows what you actually use.

Start with your city's latest annual water quality report, often called a Consumer Confidence Report. Community water systems publish one every year. Look for total hardness, usually in the section on taste, odor and other aesthetic parameters. For Mesa, also check the zone map in the report. If you are in Chandler, use the FAQ average or ask the city's water quality staff which supply your area receives. If you are on a private well or a small water company, the utility report will not apply and a lab test is the only reliable answer.

Then confirm with a test at the tap. Home test strips give a quick read. For a softener setup or a persistent scale problem, a lab test is better. Test the cold water before it reaches any softener you already own.

We size and set up softeners across the Valley, and we give an upfront price before work starts. If you would rather have someone measure your hardness and tell you plainly whether a softener makes sense, that is a free estimate.

Here are the short versions of the questions people ask most.

Is any Phoenix-area water soft? Not in the sources above. The lowest single reading listed is Chandler's low of 5 grains per gallon, which the USGS scale rates as moderately hard.

Is hard water safe to drink? Yes. Phoenix describes hardness as a harmless aesthetic issue, and Tempe notes no federal standard applies to it. It is a scale and soap problem, not a health one. For the health side of water, see the primary standards in your city's report.

Does my zone matter? In Mesa, yes: about 12 grains per gallon in the City Zone versus about 16 in the Eastern and Southern zones. In other cities, your supply blend matters more than your street.

Should I trust an online hardness map by ZIP code? Use it as a rough hint at most. Those maps often blend old data. Your utility's current report and a test at your own tap are the sources that count.