Weld County Well Water Testing
Private-well guidance for Weld County, Colorado: USGS area-risk estimates for arsenic and nitrate, a recommended test panel, and how to get your own well tested at a Colorado-certified lab.
Weld County groundwater risk (area estimates)
These are modeled USGS estimates for the county area — not a measurement of your specific well.
Arsenic
area estimate7%
modeled chance a well in this area exceeds 10 µg/L (the EPA limit).
17% chance of exceeding 5 µg/L.
Most-probable concentration category: <=5 ug/L.
Nitrate
area estimate2.10 mg/L
predicted nitrate (as N) for domestic-supply depth.
This estimate is below the 10 mg/L EPA limit, but individual wells can still exceed it.
Private wells
area estimate18,704
people on private wells in Weld County.
Roughly 7,482 households, estimated from the USGS modeled domestic-supply population.
Area context
Additional state-only or optional layers for Weld County, shown where the data exists.
Uranium
area estimateA state-only uranium model is not available for Colorado. See observed samples and test your own well to learn its uranium level.
Radon
area estimateA state-only radon model is not available for Colorado. See observed samples and test your own well to learn its radon level.
Agricultural land use
area contextAbout 11% of the Weld County area is row-crop farmland (USDA Cropland Data Layer). Intensively farmed row-crop land raises the likelihood of elevated nitrate in nearby groundwater, so it is a reason to include nitrate in your test panel. This is land-use context for the county area — not a measurement of nitrate in any well.
PFAS
public-system proxyNo PFAS were detected above EPA reporting limits in the 20 public water systems tested in Weld County under the EPA's national PFAS monitoring program (UCMR5).
This reflects PFAS detections in public water systems near Weld County — a regional proxy, not a measurement of private wells. If you rely on a private well, only a lab test of your own water reveals its PFAS level.
These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
Recommended test panel for Weld County
- coliform
Coliform bacteria is recommended for every private well as the universal baseline test. The federal loan minimum (FHA, VA, USDA) tests for coliform, nitrate, nitrite, lead.
Federal FHA, VA, and USDA home loans require testing for coliform, nitrate, nitrite, lead at the point of a federally-backed loan. See the program-specific rules: FHA well test, VA well test, USDA well test.
Already have lab results? Interpret your well water test results to see how your own numbers compare to EPA limits.
How Weld County compares across Colorado
Where Weld County's modeled area estimates sit relative to the other Colorado counties in our analysis.
- Arsenicabove the Colorado median
Weld County: 7% · Colorado median: 4% · flagged in 9 of 63 counties.
See all Colorado arsenic data → - Nitrateabove the Colorado median
Weld County: 2.10 mg/L · Colorado median: 0.42 mg/L · flagged in 1 of 63 counties.
See all Colorado nitrate data →
Municipal (public) water in Weld County
Most Weld County residents are served by a public water system, not a private well. If that's you, open your city's tap-water quality report:
+ 11 more — search every city.
Prefer a Simpler Option?
Can't find a convenient local lab? Mail-in testing offers EPA-certified analysis without appointments or travel.
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Standard Home Water Test
$232
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SimpleLab
Advanced Home Water Test
$369
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Tap Score
Volatile Organic Compounds (VOC) Test
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Detects volatile organic compounds including industrial solvents, fuels, and chemical contaminants.
Find a state-certified lab
Test your Weld County well through a lab certified by the Colorado Department of Public Health & Environment — find one in the official directory (Online searchable database—select "Drinking Water" matrix).
Recognize & research well-water problems
Notice a problem? Diagnose it by symptom
Learn about these contaminants in drinking water
Data sources
Weld County's estimates are modeled from public federal datasets. See the data & methodology for how we build, source, and validate them.
- USGS arsenic probability-of-exceedance model
- USGS nitrate predicted concentration, domestic-supply depth
- USGS domestic (private) well population density
- USDA NASS Cropland Data Layer (CDL) 30m
- EPA UCMR5 PFAS occurrence in public water systems (Fifth Unregulated Contaminant Monitoring Rule)
- EPA/USGS Water Quality Portal (waterqualitydata.us)
- US Census TIGER/Line county polygons
By TapWaterData Editorial · Last updated June 26, 2026.
Weld County well water FAQ
How do I test my well water in Weld County?
Order a sample kit covering the recommended panel for Weld County (coliform), then send it to a Colorado-certified drinking-water laboratory. Certified labs use EPA-approved methods, so the results are defensible for a federally-backed home loan. You can also use a mail-in test kit for a convenient EPA-certified analysis.
What does the USGS arsenic estimate mean for my well?
It is an area estimate, not a prediction for your specific well. The USGS model describes how likely elevated arsenic is across Weld County as a whole; an individual well in the county can be much higher or much lower. Only testing your own well reveals its actual arsenic level.
How often should a private well be tested?
The CDC recommends testing private wells at least once a year for total coliform bacteria and nitrate, and more often if you notice a change in taste, color, or odor, or after flooding or nearby construction.
Does Colorado require well testing?
Federal FHA, VA, and USDA home-loan programs require a private-well water test at the point of a federally-backed loan. A state sale, rental, or recurring testing mandate was not independently verified for this state — consult your state's program.
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