Free testing, with limits
Colorado tests private wells for PFAS for free, but not for anything else. Check which tests it includes before you count on it for nitrate.
Colorado's private well pageNitrate in Colorado well water, by county
Nitrate is widespread, over the limit in 15% or more of tested wells, in 5 of the 22 Colorado counties with 10 or more tested wells. 4 more look high, but those results likely overstate it. 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 Colorado compares with the rest of the country
Across Colorado, about 1 in 10 tested wells had nitrate over the EPA limit of 10 mg/L (103 of 1,004). Across all tested wells in the US it's about 1 in 12. Colorado is about average, so the county you live in tells you more than the state does.
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 |
|---|---|---|---|
| Weld County | 21 | Widespread | |
| Alamosa County | 23 | Widespread | |
| Adams County | 36 | Widespread | |
| Montrose County | 38 | Widespread | |
| Mesa County | 15 | Widespread | |
| Arapahoe County | 67 | Widespread | |
| Montezuma County | 24 | Widespread | |
| Pueblo County | 18 | Widespread | |
| Rio Grande County | 20 | Widespread | |
| Saguache County | 14 | Worth checking | |
| El Paso County | 105 | Worth checking | |
| Elbert County | 30 | Rare | |
| Douglas County | 35 | Rare | |
| Park County | 248 | Rare | |
| Eagle County | 97 | Rare | |
| Rio Blanco County | 26 | Rare | |
| Chaffee County | 22 | Rare | |
| Garfield County | 20 | Rare | |
| Otero County | 19 | Rare | |
| La Plata County | 18 | Rare | |
| Lake County | 18 | Rare | |
| Grand County | 12 | Rare |
* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:
- Weld County: All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.
- Alamosa County: Almost all of these tests come from the US Geological Survey, mostly before 2013, so this likely overstates it.
- Mesa County: All of these tests come from the US Geological Survey, mostly before 2013 in one small part of the county, so this likely overstates it.
- Rio Grande County: Almost all of these tests come from the US Geological Survey, mostly before 2013 in one small part of the county, so this likely overstates it.
20 more Colorado counties have 1 to 9 tested wells for nitrate, too few to rate.
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Where to get your well tested for nitrate in Colorado
A lab Colorado certifies
Ask for nitrate by name. Results from a certified lab count for a home sale or a loan.
Labs certified by ColoradoA 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 Colorado
- Well water testing in Colorado: 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 Colorado wells, by county
- Uranium in Colorado wells, by county
- Manganese in Colorado wells, by county
- Lead in Colorado wells, by county
Questions people ask about nitrate in Colorado
Is there nitrate in Colorado well water?
Nitrate is widespread, over the limit in 15% or more of tested wells, in 5 of the 22 Colorado counties with 10 or more tested wells. 4 more look high, but those results likely overstate it. Across Colorado, about 1 in 10 tested wells had nitrate over the EPA limit of 10 mg/L (103 of 1,004). Across all tested wells in the US it's about 1 in 12. Colorado is about average, so the county you live in tells you more than the state does.
Where can I get my well tested for nitrate in Colorado?
Colorado tests private wells for PFAS for free, but not for anything else. If that doesn't cover you, use a lab certified by Colorado for drinking water, or a mail-in kit that includes nitrate from a certified lab.
See Colorado'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 Public Health and Environment.