Well water in El Paso County, Colorado
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Testing strongly recommended
tested well samples in El Paso County exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
8,158 test results across 13 contaminants from at least 630 wells, 1954 to 2025; nitrate has the most at 2,049. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 37,721 people in El Paso County get their drinking water from a private well, per USGS 2015 county water use. That is about 6% of residents.
Separately, the USGS national arsenic model estimates that 4% of the 37,721 people on private wells in El Paso County draw water above 10 ug/L (the model's range is 3% to 5%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside El Paso County. 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 1954 to 2025 | 2,049 | 97% | 8.9 | 3,980 | 10 mg/L EPA limit | |
| PFOA 2021 to 2025 | 60 | 22% | 0 | 52.4 | 4 ng/L EPA limit | |
| Radium (226 + 228) 1979 to 1982 | 12 | 100% | 0.15 | 6.7 | 5 pCi/L EPA limit | |
| PFOS 2021 to 2025 | 60 | 3% | 0 | 14.8 | 4 ng/L EPA limit | |
| Lead 1973 to 2025 | 341 | 34% | 0 | 200 | 15 ug/L EPA limit | |
| Fluoride 1954 to 2025 | 1,081 | 99% | 0.7 | 7.6 | 4 mg/L EPA limit | |
| Uranium 1979 to 2025 | 164 | 93% | 1.74 | 32 | 30 ug/L EPA limit | |
| Arsenic 1976 to 2025 | 376 | 27% | 0 | 9 | 10 ug/L EPA limit | |
| Copper 1973 to 2025 | 340 | 61% | 0.001 | 0.048 | 1.3 mg/L EPA limit | |
| Chloride 1954 to 2025 | no limit | 1,628 | 100% | 31 | 1,800 | 250 mg/L nuisance level |
| Manganese 1971 to 2025 | no limit | 1,042 | 71% | 2 | 7,000 | 300 ug/L health guideline |
| Iron 1955 to 2025 | no limit | 988 | 75% | 14.3 | 130,000 | 300 ug/L nuisance level |
| Radon 2004 to 2005 | no limit | 17 | 100% | 1,300 | 4,610 | 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 | 50%1,186 samples | 38%302 samples | 44%340 samples | 37%221 samples |
| Fluoride | <1%875 samples | 0%25 samples | 0%85 samples | 0%96 samples |
| Arsenic | 0%291 samples | 0%25 samples | n/a | 0%60 samples |
| Lead | 2%256 samples | 0%25 samples | n/a | 0%60 samples |
| Copper | 0%255 samples | 0%25 samples | n/a | 0%60 samples |
| Uranium | 4%25 samples | 0%25 samples | 0%35 samples | 0%79 samples |
Nitrate above the limit in El Paso County fell from 44% of 340 samples in the 2010s to 37% of 221 in the 2020s.
Fluoride, arsenic, lead, copper, uranium have held within a few points between the two most recent periods with enough samples.
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
The contaminants most often above their limit here are nitrate (46% of 2,049 samples), pfoa (20% of 60 samples), and radium (226 + 228) (8% of 12 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, Manganese, and Iron 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 El Paso County
- 1Nitrate46% of 2,049 local samples were above the limit.
- 2PFOA20% of 60 local samples were above the limit.
- 3Radium (226 + 228)8% of 12 local samples were above the limit.
- 4PFOS3% of 60 local samples were above the limit.
- 5Lead1% of 341 local samples were above the limit.
- 6Fluoride<1% of 1,081 local samples were above the limit.
- 7Uranium<1% of 164 local samples were above the limit.
Test your El Paso County well for nitrate, PFOA and radium (226 + 228)
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 Colorado: certified labs, state programs and prices.
Already have results back? Get your lab report read against the El Paso County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under El Paso County
Denver Basin aquifer system
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 county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Colorado
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.
Contamination sources on record in El Paso County
CDPHE operating landfills records 3 regulated sites in El Paso County, among 3 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 3
- lined landfills and transfer facilities
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
PFOS
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Lead
Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
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 PFOA
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 PFOA
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOA
Aquasana HealthShield whole-house filter
whole-house, at the point of entry, about $2,099
Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
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Common questions
Is there arsenic in well water in El Paso County?
Arsenic was detected in 27% of 376 public well samples in El Paso County, and 0% 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 El Paso County?
The median radon level across 17 public samples in El Paso County was 1,300 pCi/L, with a high of 4,610 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in El Paso County?
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 near El Paso County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Colorado dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 8,158 samples in El Paso County. 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 37,721 people on private wells in El Paso County 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.
- CDPHE operating landfills: 3 regulated sites located in El Paso County. Operating commercial landfills from the Colorado Department of Public Health and Environment. Retrieved September 18, 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.