Nitrate and arsenic are worth checking in Navajo County wells.
2 worth checking, 5 rare out of 7 health checks.
From 153 wells tested in Navajo County since 2000; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
5 in 10 people 55,863 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 Navajo County compares with Arizona and the counties around it.
Each result puts Navajo County next to the 5 counties that border it, on the chart's 0 to 50% scale.
These 2 are worth checking in Navajo County.
Nitrate15 of 125 wells over
Arsenic8 of 81 wells over
These 5 are rare in Navajo County.
Manganese4 of 117 wells over
Lead1 of 62 wells over
Fluoride0 of 50 wells over
Uranium0 of 20 wells over
Too few tested to show: Apache, Gila, Graham.
Radon in water0 of 20 wells over
Too few tested to show: Apache, Coconino, San Juan, UT.
Coliform bacteria turned up in 6 of 14 tested Navajo County wells, so test for it every year.
Coliform bacteria6 of 14 wells had it
Too few tested to show: Apache, Gila, Graham, San Juan, UT.
E. coli4 of 15 wells had it
Too few tested to show: Apache, Gila, Graham, San Juan, UT.
E. coli means human or animal waste is getting in, so if a test of your Navajo County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 7 of 81 tested wells, and it isn't a health risk.
Iron stains7 of 81 wells had it
About 4 in 10 of the 153 wells tested in Navajo County have a test from 2020 or later.
With 58 wells tested since 2020, age matters less here than who did the testing and why.
Most Navajo 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 3 things to check in Navajo County.
- Bacteria
- Nitrate
- Arsenic
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 370 feet.
That comes from 4,026 household wells in Arizona's drilling records. Most wells of every kind here are 200 to 450 feet deep. Wells as deep as Navajo 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. Typical household wells here go deeper than in 11 of the 14 other 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 Navajo County.
Navajo 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 8 town water systems in Navajo County test for PFAS. 2 found some PFAS, all below the new limits. Only 6 wells in Navajo County have 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 Navajo County
Is well water in Navajo County safe to drink?
15 of 125 wells tested in Navajo County had nitrate over the limit, about 1 in 8. Across Arizona it's about 1 in 7. That's a bigger share than in 8 of the 14 other Arizona counties with 10 or more tested wells. So test your own well for nitrate before you count on it.
Where can I get my well tested in Navajo 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 and arsenic, the tests that matter most in Navajo County.
How deep are wells in Navajo County?
Half the household wells here are shallower than 370 feet. Typical household wells here go deeper than in 11 of the 14 other Arizona counties with enough drilling records.
How does Navajo County compare with the counties around it?
For nitrate, the share of tested wells over the limit: 1 of the 5 neighboring counties with data had a higher share than Navajo County, at 12%. Graham had the most, at 16%. Groundwater doesn't stop at county lines, so Graham's 16% is worth knowing about if you live near it.
How often should I test my well in Navajo County?
In Navajo County, 6 of 14 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 Navajo County numbers come from
- People on wells: 55,863 in Navajo County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,022 well water samples from 153 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2026.
- Well depths: 4,026 Arizona drilling records for Navajo County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 5 counties that share a border with Navajo County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 8 town water systems in Navajo County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Navajo County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Department of Health Services, checked November 1, 2026.