Your county health department
Arizona doesn't run a statewide free testing program that we know of. Some county health departments test wells or sell kits, so call yours first.
Arizona's private well pageNitrate in Arizona well water, by county
Nitrate is widespread, over the limit in 15% or more of tested wells, in 6 of the 15 Arizona counties with 10 or more tested wells. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.
How Arizona compares with the rest of the country
Across Arizona, about 1 in 7 tested wells had nitrate over the EPA limit of 10 mg/L (234 of 1,719). Across all tested wells in the US it's about 1 in 12. So nitrate turns up somewhat more often in Arizona than in the country as a whole. Check your county below.
Why it matters: It's dangerous for babies under 6 months, because it keeps their blood from carrying enough oxygen.
Nitrate soaks down into groundwater from fertilizer, manure and septic systems.
Nitrate in tested wells, county by county
Share of each county's tested wells with at least one result over the EPA limit of 10 mg/L. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.
| County | Wells tested | Wells over the limit | Level |
|---|---|---|---|
| La Paz County | 24 | Widespread | |
| Maricopa County | 451 | Widespread | |
| Yuma County | 83 | Widespread | |
| Pinal County | 60 | Widespread | |
| Mohave County | 199 | Widespread | |
| Graham County | 25 | Widespread | |
| Navajo County | 125 | Worth checking | |
| Yavapai County | 132 | Worth checking | |
| Cochise County | 156 | Worth checking | |
| Greenlee County | 26 | Worth checking | |
| Santa Cruz County | 40 | Worth checking | |
| Pima County | 107 | Rare | |
| Gila County | 150 | Rare | |
| Coconino County | 86 | Rare | |
| Apache County | 55 | Rare |
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Where to get your well tested for nitrate in Arizona
A lab Arizona certifies
Ask for nitrate by name. Results from a certified lab count for a home sale or a loan.
Labs certified by ArizonaA mail-in kit
Fill the bottles at your kitchen tap and mail them back. We mark the kits that include nitrate.
Compare kitsKeep reading about wells in Arizona
- Well water testing in Arizona: how to get tested and what turns up statewide
- Nitrate in well water: where it comes from, what it does and how to remove it
- Arsenic in Arizona wells, by county
- Uranium in Arizona wells, by county
- Manganese in Arizona wells, by county
- Lead in Arizona wells, by county
- Radon in Arizona wells, by county
Questions people ask about nitrate in Arizona
Is there nitrate in Arizona well water?
Nitrate is widespread, over the limit in 15% or more of tested wells, in 6 of the 15 Arizona counties with 10 or more tested wells. Across Arizona, about 1 in 7 tested wells had nitrate over the EPA limit of 10 mg/L (234 of 1,719). Across all tested wells in the US it's about 1 in 12. So nitrate turns up somewhat more often in Arizona than in the country as a whole. Check your county below.
Where can I get my well tested for nitrate in Arizona?
Use a lab certified by Arizona for drinking water, or a mail-in kit that includes nitrate from a certified lab. Some county health departments test wells too, so call yours first.
See Arizona's list of certified labs, or compare mail-in kits.
Where these numbers come from
- Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over the EPA limit of 10 mg/L. Wells tested for studies and monitoring, not a random sample of homes.
- Likely overstated: our own check of who tested the wells, when and where. How we check.
- State programs and links: Department of Health Services.