Well water in Wyoming
1in7
Testing recommended
tested well samples in Wyoming exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
31,802 test results across 13 contaminants from at least 3,269 wells, 1911 to 2026; nitrate has the most at 8,356. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 119,066 people in Wyoming get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that 5% of the 119,066 people on private wells in Wyoming draw water above 10 ug/L (the model's range is 4% to 7%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Wyoming. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Nitrate 1911 to 2026 | 8,356 | 84% | 0.7 | 2,440 | 10 mg/L EPA limit | |
| Uranium 1954 to 2018 | 710 | 85% | 1.8 | 1,730 | 30 ug/L EPA limit | |
| Arsenic 1973 to 2018 | 1,110 | 58% | 1 | 64,000 | 10 ug/L EPA limit | |
| Fluoride 1917 to 2026 | 4,254 | 97% | 0.5 | 130 | 4 mg/L EPA limit | |
| Radium (226 + 228) 1975 to 2017 | 299 | 94% | 0.14 | 438 | 5 pCi/L EPA limit | |
| Lead 1973 to 2018 | 1,095 | 29% | 0 | 1,300 | 15 ug/L EPA limit | |
| Copper 1973 to 2018 | 1,063 | 54% | 0 | 1.4 | 1.3 mg/L EPA limit | |
| E. coli 1998 to 2017 | 415 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1911 to 2026 | no limit | 5,029 | 99% | 9.6 | 121,000 | 250 mg/L nuisance level |
| Sodium 1923 to 2026 | no limit | 4,317 | 100% | 85 | 75,700 | 20 mg/L health guideline |
| Iron 1924 to 2026 | no limit | 3,223 | 80% | 60 | 900,000 | 300 ug/L nuisance level |
| Manganese 1950 to 2026 | no limit | 1,660 | 70% | 11 | 15,600 | 300 ug/L health guideline |
| Radon 1995 to 2017 | no limit | 271 | 98% | 690 | 33,400 | 2,000 pCi/L health guideline |
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 16%5,743 samples | 15%1,396 samples | 7%889 samples | 4%328 samples |
| Fluoride | 8%3,392 samples | 2%244 samples | 2%497 samples | 0%121 samples |
| Arsenic | 11%528 samples | 9%147 samples | 3%435 samples | n/a |
| Lead | 6%516 samples | 0%147 samples | <1%432 samples | n/a |
| Copper | <1%484 samples | 0%147 samples | 0%432 samples | n/a |
| Uranium | 12%141 samples | 10%135 samples | 10%434 samples | n/a |
Arsenic above the limit in Wyoming fell from 9% of 147 samples in the 2000s to 3% of 435 in the 2010s.
Nitrate, fluoride, lead, copper, uranium have held within a few points between the two most recent periods with enough samples.
What this means
The contaminants most often above their limit here are nitrate (14% of 8,356 samples), uranium (10% of 710 samples), and arsenic (8% of 1,110 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Wyoming
- 1Nitrate14% of 8,356 local samples were above the limit.
- 2Uranium10% of 710 local samples were above the limit.
- 3Arsenic8% of 1,110 local samples were above the limit.
- 4Fluoride7% of 4,254 local samples were above the limit.
- 5Radium (226 + 228)6% of 299 local samples were above the limit.
- 6Lead3% of 1,095 local samples were above the limit.
- 7Copper<1% of 1,063 local samples were above the limit.
Test your Wyoming well for nitrate, uranium and arsenic
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Wyoming: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Wyoming numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the Wyoming report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
The rock under Wyoming
Lower Tertiary aquifers
Sandstone. Sandstone wells draw from pore space in the rock and tend to be dependable. Iron, manganese and hardness are common, and some sandstones carry arsenic or radium, so a first test should include both.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the state centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Wyoming
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Know Your Well, Wyoming DEQ
- Certified Drinking Water Laboratories for Systems in Wyoming (EPA Region 8), EPA Region 8
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For uranium
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For lead
Aquasana Claryum 3-Stage under-sink filter
under-sink or countertop, about $175
Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
Common questions
Is there arsenic in well water in Wyoming?
Arsenic was detected in 58% of 1,110 public well samples in Wyoming, and 8% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Wyoming?
The median radon level across 271 public samples in Wyoming was 690 pCi/L, with a high of 33,400 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Wyoming?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Counties in Wyoming
- Albany6% uranium
- Big Horn8% nitrate
- Campbell10% arsenic
- Carbon12% arsenic
- Converse30% uranium
- Crook6% nitrate
- Fremont4% nitrate
- Goshen49% nitrate
- Hot Springs14% nitrate
- Johnson21% nitrate
- Laramie16% nitrate
- Lincoln10% nitrate
- Natrona25% nitrate
- Niobrara24% nitrate
- Park13% arsenic
- Platte16% uranium
- Sheridan10% uranium
- Sublette9% fluoride
- Sweetwater53% fluoride
- Teton5% fluoride
- Uinta11% nitrate
- Washakie13% nitrate
- Weston4% nitrate
Want the numbers themselves? Download the Wyoming dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 31,802 samples in Wyoming. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 119,066 people on private wells in Wyoming above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.