Phoenix Water Hardness by City and Utility: Grains per Gallon From Official Reports

Is Phoenix water hard?

Yes. The City of Phoenix's 2025 water quality report lists total hardness of 172 to 302 ppm, or 10 to 17.6 grains per gallon, from distribution-system samples. On the University of Nebraska-Lincoln Extension scale, 10.5 gpg (180 mg/L) and above is very hard, so almost all of that range is very hard and the low end is hard.

That range describes the whole city system, not your address. Phoenix blends Salt, Verde and Colorado river water with a little groundwater, so the hardness at your tap depends on which supply reaches your neighborhood, and when. A test at your faucet gives the number to set a softener to.

Hard water isn't just a Phoenix issue. Most other Valley cities we checked report averages or ranges from about 9 gpg (Peoria, third-party listing) up to a 16.5 gpg citywide average in Chandler. The City of Surprise is the low exception: its three 2025 system reports average 3.9 to 6.2 gpg. For a Phoenix install, see water softener installation in Phoenix.

Which utility serves your ZIP code or address?

Your hardness depends on which water system serves your address, which doesn't always match the city on your mail. We haven't published a ZIP-by-ZIP map because ZIP codes cross utility lines.

From each city's or utility's own report or website, except Peoria's PWSID and source, which come from the TapWaterData listing.

The quickest check is your water bill: it names your provider. Then open that provider's annual water quality report, or use the EPA's Consumer Confidence Report locator to find it. Enter that report's hardness into the table above, or test your tap.

Why is Phoenix water so hard?

Phoenix-area water is hard because its sources pick up calcium and magnesium from the rock and soil they flow through. Valley cities draw on Salt and Verde river water (SRP), Colorado River water (CAP) and groundwater from wells. Each has a different mineral profile, and most cities blend them, so hardness shifts by area and season.

The three main sources:

Salt and Verde rivers (SRP)

Snowmelt and runoff stored in reservoirs and delivered by Salt River Project canals. Tempe notes the Verde tends to be higher in hardness, while the Salt runs higher in dissolved solids and chlorides.

Colorado River (CAP)

Delivered across the desert by the Central Arizona Project aqueduct. Mesa's eastern and southern zones, served by CAP water, average 16 gpg compared with about 12 in the SRP-served City Zone.

Groundwater

Pumped from wells. The EPCOR San Tan system relies on groundwater alone and reports 15 to 18 gpg. Buckeye relies almost entirely on wells, and Surprise's city systems pump groundwater from 19 wells but report far lower hardness, which shows that well water isn't always harder.

The City of Phoenix explains that hardness comes from minerals like calcium and magnesium in the soils that source water contacts. Because the blend changes with the seasons and drought conditions, your hardness can shift through the year.

Why hardness can change through the year

• Runoff. Tempe says its source mix changes seasonally and year to year with precipitation and mountain snowmelt; the Verde runs harder, the Salt higher in dissolved solids.
• Canal dry-outs. Gilbert pumps more groundwater during high demand and when canals are dried out for maintenance, which can change what reaches your tap.
• Blending. Phoenix blends CAP and SRP water partly to improve aesthetics, and Mesa serves different zones from different rivers.

How to test your water hardness at home

1. Check your city's report. Search your city or utility name plus "water quality report". It lists hardness as a range or average for the whole system.
2. Use a test strip or drop kit. Hardware stores sell inexpensive hardness strips. Run cold water for a minute, test at a faucet before any filter, and read the result in gpg or mg/L.
3. Test before and after an existing softener. If you already have one, compare a hose bib or the bypass setting with a kitchen tap to see whether it is working.
4. Ask for a professional test. HomeAdvisor lists water testing at about $30 to $500, depending on whether you use a DIY kit or a professional. Some water treatment companies include a basic test in a quote visit; ask whether there is any charge when you book.

If your result is in mg/L or ppm, divide by 17.1 to get grains per gallon.

What hard water does to Arizona homes: water heaters, coolers and drip lines

In the Valley, hard water shows up in a few places that homeowners in milder climates rarely think about. Here is what local utilities and fact sheets say, and what you can do about it.

Water heaters

Scale settles in the tank and on heating elements, which lowers efficiency over time. Chandler suggests flushing a water heater every six months without a softener and once a year with one. Scottsdale's hard water fact sheet suggests a 120 to 125 degree setting, since hotter water leaves more mineral residue.

Evaporative (swamp) coolers

Coolers work by evaporating water, which leaves minerals behind in the pads and pan. A water hardness fact sheet hosted by the City of Goodyear says that with hard water you may need to change cooler pads twice a season. It recommends keeping the bleed-off valve adjusted so fresh water keeps circulating, or, if there is no bleed-off, flushing the cooler with fresh water once or twice a season.

Drip irrigation and outdoor fixtures

The same fact sheet notes that hard water deposits can clog irrigation emitters as water evaporates. Outdoor lines are usually left on unsoftened water, since softened water adds sodium that University of Arizona Extension says isn't suited to salt-sensitive plants, so emitters and hose bibs need their own cleaning.

Fixtures, glass and dishes

• White crust on faucets and shower heads
• Cloudy spots on glasses and shower glass
• Soap scum that comes back fast
• Dishwashers and coffee makers that scale up (Scottsdale suggests running white vinegar through them every few months)

If you are weighing options, start with our guides to water softener cost and reverse osmosis systems for drinking water, or browse every city on our water softener service areas page.