Where Does Arizona Tap Water Come From?

Turn on a faucet in Mesa, Gilbert or Chandler and the water may have started as snow in the forests of northern Arizona, or in the Rocky Mountains, or deep underground. The East Valley uses three sources, and most homes get a blend.

Real OX Plumbing job: Under-sink reverse osmosis drinking water system installed next to a garbage disposal.

Source 1: Salt and Verde Rivers (SRP)

Snow and rain fall on the Salt and Verde watersheds, about 8.3 million acres of forest in northern and eastern Arizona. In spring the snow melts into the rivers, and SRP stores it in seven reservoirs:

On the Salt River: Theodore Roosevelt Lake (behind Roosevelt Dam, which SRP calls Arizona's first dam), Apache Lake, Canyon Lake and Saguaro Lake
On the Verde River: Horseshoe Lake and Bartlett Lake
On East Clear Creek: C.C. Cragin Reservoir

So yes: Saguaro Lake and Canyon Lake, where people go boating, are part of the same system that supplies Valley cities. The dams release water down the river to Granite Reef Diversion Dam, where it enters SRP's 131 miles of canals. Those canals carry it to city treatment plants and to irrigation customers. SRP says the water travels about 150 miles from source to home.

Source 2: The Colorado River (CAP)

The Central Arizona Project pulls Colorado River water out of Lake Havasu, near Parker, and moves it through a 336-mile system of aqueducts, tunnels, pumping plants and pipelines to Maricopa, Pinal and Pima counties. That water started as snow in the Colorado River basin, much of it in the Rocky Mountains. It's the supply being cut in 2027 and 2028; see what the Colorado River cuts mean for your home.

Source 3: Groundwater

Water stored underground in aquifers is pumped up through wells. SRP runs about 270 high-capacity wells, and the cities run their own. Several East Valley cities have also stored extra river water underground for dry years.

Who gets what

Each city publishes its own mix, and it changes year to year:

Mesa: about 53% Colorado River, 40% Salt and Verde Rivers, 7% groundwater. Mesa's Val Vista plant treats SRP water; the Brown Road and Signal Butte plants treat CAP water. Which one reaches you depends on where you live.
Chandler: about 57% Salt and Verde Rivers, 37% Colorado River, 6% groundwater.
Gilbert: river water from SRP and CAP, plus wells.
Scottsdale: Colorado River water through CAP, Salt and Verde River water, groundwater and reclaimed water.

A citywide average can't tell you exactly which lake your glass came from; blending changes with the season. For the system that serves your street, get a free water report for your address.

Why the water is so hard

All three sources pick up calcium and magnesium from rock and soil along the way. City treatment makes the water safe to drink; it doesn't take those minerals out. Mesa reports hardness from 12 to 22 grains per gallon, depending on the source serving your area. The U.S. Geological Survey calls anything over 10.5 "very hard."

Hard water isn't a health problem. It's a plumbing problem: scale in water heaters, crusty faucets and showerheads, and spots on glass. The fixes are a water softener or a salt-free conditioner; see which one fits and water treatment. Your city's numbers are on our Mesa, Gilbert, Chandler and Scottsdale pages.

Where your plumbing starts

The city's job ends at the meter. Past that, the pipes, valves, water heater and fixtures are yours, and that's where hard water and leaks show up. OX Plumbing works on that side across Mesa and the East Valley. Our $99 service call covers the visit, the diagnosis and an upfront price.

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Where Does East Valley Tap Water Come From? From Roosevelt Lake to Your Faucet