Quick answer
About 113,000 people in Wyoming (20.0% of residents) got their water from private wells in 2010, according to USGS estimates. Wyoming Department of Environmental Quality runs the state’s private well guidance. Wyoming DEQ's PFAS in Drinking Water Monitoring Assistance Program provides cost-free PFAS sampling for private well owners near known or suspected PFAS sources.
- People on private wells
- 112,590
- Share of residents
- 20.0%
- Rank among states
- 44th
- Well users modeled above 10 µg/L arsenic
- 5.5%
Where to get your well tested in Wyoming
- Wyoming Department of Environmental Quality: Know Your Well, the state’s guidance for private well owners.
Free or low-cost testing
Wyoming DEQ's PFAS in Drinking Water Monitoring Assistance Program provides cost-free PFAS sampling for private well owners near known or suspected PFAS sources. (source)
Mail-in lab kits are another option when no local lab is convenient. See well water test kits for what home kits can and can’t tell you.
What to test for
- Every year: total coliform bacteria and nitrate.
- Before buying equipment: pH, hardness, iron, manganese and, if there’s a smell, hydrogen sulfide.
- Based on location: arsenic, uranium and radon, PFAS, and lead in older plumbing.
USGS modeling estimates that about 5.5% of Wyoming’s private well users have water above the 10 µg/L arsenic limit. Arsenic has no taste or smell, so include it in your first test.
Private wells by county
Estimated people relying on private wells in each Wyoming county in 2010, the share of residents that represents, and the modeled share of well users with arsenic above 10 µg/L. These are USGS model estimates (2010 population), not measurements of any well. Arsenic is hidden for counties with fewer than 500 well users.
| County | People on wells | Share | Arsenic >10 µg/L |
|---|---|---|---|
| Laramie County | 17,493 | 19.1% | 4.3% |
| Fremont County | 12,293 | 30.6% | 9.0% |
| Park County | 9,323 | 33.1% | 6.5% |
| Campbell County | 8,621 | 18.7% | 3.9% |
| Sheridan County | 7,872 | 27.0% | 4.7% |
| Sublette County | 5,533 | 54.0% | 7.5% |
| Lincoln County | 5,184 | 28.6% | 4.0% |
| Natrona County | 5,139 | 6.8% | 4.0% |
| Goshen County | 4,389 | 33.1% | 5.8% |
| Teton County | 4,258 | 20.0% | 4.2% |
| Albany County | 4,206 | 11.6% | 2.8% |
| Uinta County | 4,015 | 19.0% | 9.7% |
Show all 23 counties
| Converse County | 3,737 | 27.0% | 4.7% |
| Sweetwater County | 3,220 | 7.4% | 11.2% |
| Platte County | 3,089 | 35.6% | 4.3% |
| Crook County | 3,082 | 43.5% | 3.7% |
| Johnson County | 2,338 | 27.3% | 4.4% |
| Big Horn County | 2,317 | 19.9% | 5.7% |
| Carbon County | 2,071 | 13.0% | 3.5% |
| Washakie County | 2,071 | 24.3% | 5.7% |
| Weston County | 1,065 | 14.8% | 4.0% |
| Niobrara County | 738 | 29.7% | 4.0% |
| Hot Springs County | 536 | 11.1% | 5.2% |
Counties with the highest modeled arsenic share: Sweetwater County (11.2%), Uinta County (9.7%), Fremont County (9.0%), Sublette County (7.5%), Park County (6.5%).
After you get results
Enter your numbers in the test results tool to see what needs treating and in what order. The guide to reading a well water test explains units and limits.
Common questions
Does Wyoming offer free well water testing?
Wyoming DEQ's PFAS in Drinking Water Monitoring Assistance Program provides cost-free PFAS sampling for private well owners near known or suspected PFAS sources.
Who oversees private wells in Wyoming?
Wyoming Department of Environmental Quality (Know Your Well) publishes guidance for private well owners. Private wells aren’t covered by the federal Safe Drinking Water Act, so testing and treatment are up to the owner.
How many people use private wells in Wyoming?
USGS estimates about 113,000 people, or 20.0% of the population in 2010. That ranks 44th of the states covered by the estimate.
What should I test my well for in Wyoming?
Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Arsenic is a known concern in parts of Wyoming, so add it to the first test.