Understanding Your Well Water in Arizona

Over 300,000 Arizonans rely on private domestic wells for their drinking water — and that water is unregulated. Arsenic exceeds safe limits in more than 20% of Arizona wells, three times the national average. The Willcox Basin is sinking. Earth fissures are splitting the ground open. If you're on a private well, nobody is testing your water but you.

The Numbers

300,000+ Arizonans on private domestic wells

20.7% of Arizona wells exceed arsenic limits (3x national avg)

51 groundwater basins monitored by ADEQ

0 federal regulations on private well testing

Why It Matters

Arizona's geology gives us the Grand Canyon and some of the most contaminated groundwater in the United States. The Basin and Range province — a landscape of down-dropped basins filled with thousands of feet of alluvial sediment — concentrates arsenic, fluoride, and dissolved salts in groundwater as it slowly moves through mineral-rich formations in an arid climate. Low precipitation means minimal dilution. Long groundwater residence times mean more dissolution of contaminants from rock.

Unlike public water systems, private wells are not regulated by the EPA or the state of Arizona. No one tests your water, treats your water, or notifies you if something is wrong. That responsibility is entirely yours.

Arsenic

Arizona's defining well water problem. 20.7% of wells exceed the EPA limit — more than 40% in Yavapai and Pinal counties. Arsenic is colorless, odorless, and tasteless. You cannot detect it without testing.

Fluoride

The second most common health-based exceedance in Arizona groundwater. Naturally elevated in basin-fill aquifers across central and southern Arizona.

Land Subsidence

Overpumping is sinking the ground. The Willcox Basin drops 6 inches per year. Nearly 50 miles of earth fissures have cracked open. Subsidence is permanent.

The Exempt Well System

Arizona's "exempt wells" pump 35 GPM or less, are exempt from metering and reporting, and face no pumping restrictions outside AMAs. Know your well type and your rights.

Find Your Community

We've researched water quality conditions for communities across Arizona that rely on private wells. Each guide covers local geology, specific contaminants with real data, testing recommendations, and treatment options.