Arsenic and nitrate are widespread in Pinal County wells.
2 widespread, 1 worth checking, 3 rare out of 6 health checks.
From 175 wells tested in Pinal County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (4).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 4 people 98,488 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Pinal County compares with Arizona and the counties around it.
Each result puts Pinal County next to the 4 counties that border it, on the chart's 0 to 50% scale.
These 2 are widespread in Pinal County wells.
Arsenic46 of 161 wells over
Nitrate13 of 60 wells over
This one is worth checking in Pinal County.
These 3 are rare in Pinal County.
Radon in water2 of 58 wells over
Manganese2 of 162 wells over
Lead0 of 159 wells over
Too few Pinal County wells were tested for this one.
Uranium4 wells tested
Coliform bacteria turned up in 2 of 4 tested Pinal County wells, so test for it every year.
Coliform bacteria2 of 4 wells had it
E. coli1 of 4 wells had it
E. coli means human or animal waste is getting in, so if a test of your Pinal County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 6 of 162 tested wells, and it isn't a health risk.
Iron stains6 of 162 wells had it
Most of the 175 wells tested in Pinal County were last tested before 2010.
An old result shows the water as it was then, so treat these 175 wells as a starting point and test your own.
Most Pinal County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 4 things to check in Pinal County.
- Bacteria
- Nitrate
- Arsenic
- Fluoride
What Arizona offers well owners
- Free testingWe didn't find a free program for all of Arizona. Arizona's private well page
- Certified labsArizona's list of certified labs
- Well recordsWe didn't find an online search.
Half the household wells here are shallower than 480 feet.
That comes from 5,158 household wells in Arizona's drilling records. Most wells of every kind here are 265 to 745 feet deep. Wells as deep as Pinal County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. That's the deepest typical depth for household wells among the 15 Arizona counties with enough drilling records.
How to find your own well's depth
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Pinal County.
Pinal County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 16 town water systems in Pinal County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 19 ng/L of PFOA. No well in Pinal County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in Pinal County
Is well water in Pinal County safe to drink?
46 of 161 wells tested in Pinal County had arsenic over the limit, about 3 in 10. Across Arizona it's about 1 in 4. That's a bigger share than in 10 of the 14 other Arizona counties with 10 or more tested wells. So test your own well for arsenic before you count on it.
Where can I get my well tested in Pinal County?
Use a lab Arizona has certified for drinking water. Arizona's list is linked above, in the box about testing. Ask for bacteria, nitrate, arsenic and fluoride, the tests that matter most in Pinal County.
How deep are wells in Pinal County?
Half the household wells here are shallower than 480 feet. That's the deepest typical depth for household wells among the 15 Arizona counties with enough drilling records.
How does Pinal County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 2 of the 4 neighboring counties with data had a higher share than Pinal County, at 29%. Maricopa had the most, at 34%. Groundwater doesn't stop at county lines, so Maricopa's 34% is worth knowing about if you live near it.
How often should I test my well in Pinal County?
In Pinal County, 2 of 4 tested wells had coliform bacteria, so the CDC's advice matters here: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the Pinal County numbers come from
- People on wells: 98,488 in Pinal County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,121 well water samples from 175 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2026.
- Well depths: 5,158 Arizona drilling records for Pinal County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 4 counties that share a border with Pinal County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 16 town water systems in Pinal County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Pinal County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Department of Health Services, checked November 1, 2026.