Well water in Connecticut
1in6
Testing recommended
tested well samples in Connecticut exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal and Connecticut DPH and USGS arsenic and uranium survey.
16,353 test results across 13 contaminants from at least 1,709 wells, 1915 to 2025; nitrate has the most at 3,518. Data refreshed September 3, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
What individual samples found
Each row summarizes every public sample for that contaminant inside Connecticut. 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 1916 to 2025 | 3,518 | 96% | 2.58 | 170 | 10 mg/L EPA limit | |
| E. coli 2002 to 2017 | 36 | 6% | 0 | 11 | 0 MPN/100mL EPA limit | |
| Uranium 1954 to 2023 | 891 | 50% | 0.012 | 766 | 30 ug/L EPA limit | |
| Arsenic 1971 to 2023 | 1,099 | 22% | 0 | 470 | 10 ug/L EPA limit | |
| Lead 1966 to 2023 | 388 | 48% | 0 | 600 | 15 ug/L EPA limit | |
| Fluoride 1953 to 2025 | 1,182 | 62% | 0.02 | 50 | 4 mg/L EPA limit | |
| Copper 1953 to 2023 | 418 | 65% | 0 | 4 | 1.3 mg/L EPA limit | |
| Radium (226 + 228) 1954 to 2017 | 206 | 47% | 0 | 2 | 5 pCi/L EPA limit | |
| Chloride 1915 to 2025 | no limit | 2,541 | 100% | 16 | 8,300 | 250 mg/L nuisance level |
| Iron 1915 to 2025 | no limit | 2,236 | 91% | 50 | 81,000 | 300 ug/L nuisance level |
| Manganese 1953 to 2025 | no limit | 2,087 | 95% | 20 | 58,000 | 300 ug/L health guideline |
| Sodium 1953 to 2025 | no limit | 1,655 | 100% | 9.6 | 1,590 | 20 mg/L health guideline |
| Radon 1988 to 2014 | no limit | 96 | 100% | 1,400 | 650,000 | 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 | 13%2,194 samples | 23%808 samples | 22%374 samples | 17%142 samples |
| Fluoride | <1%868 samples | 0%191 samples | 0%52 samples | 0%71 samples |
| Arsenic | 2%252 samples | <1%149 samples | 3%697 samples | n/a |
| Uranium | 4%150 samples | 0%112 samples | 4%628 samples | n/a |
| Copper | <1%260 samples | 0%112 samples | 0%45 samples | n/a |
| Lead | 3%230 samples | 0%112 samples | 0%45 samples | n/a |
Nitrate above the limit in Connecticut fell from 22% of 374 samples in the 2010s to 17% of 142 in the 2020s.
Fluoride, arsenic, uranium, copper, lead 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 (17% of 3,518 samples), e. coli (6% of 36 samples), and uranium (3% of 891 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 Connecticut
- 1Nitrate17% of 3,518 local samples were above the limit.
- 2E. coli6% of 36 local samples were above the limit.
- 3Uranium3% of 891 local samples were above the limit.
- 4Arsenic3% of 1,099 local samples were above the limit.
- 5Lead2% of 388 local samples were above the limit.
- 6Fluoride<1% of 1,182 local samples were above the limit.
- 7Copper<1% of 418 local samples were above the limit.
- 8Volatile organic compounds (VOCs)11,225 leaking underground storage tank sites on record locally.
- 9Metals panel116 hazardous waste sites on record locally.
Test your Connecticut well for nitrate, E. coli and uranium
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 Connecticut: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Connecticut numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the Connecticut report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in Connecticut
3,681 domestic wells in Connecticut are on record with the state since 1925. the typical well is 350 feet deep (one in ten goes past 600 feet).
In a typical Connecticut well, the median yield is 8.5 gallons per minute, 17% of wells yield under 3 gallons per minute and usually need a storage tank.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open Connecticut well completion reports and choose Water Well.
- The report lists depth, depth to rock, casing, static water level and yield.
Only reports filed online since January 2021 are here; older paper reports are held by the Department of Consumer Protection.
The rock under Connecticut
Early Mesozoic basin 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 Connecticut
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.
- Private Wells, CT DPH
- Environmental Laboratory Certification, CT DPH
Contamination sources on record in Connecticut
CT DEEP contaminated sites and landfills records 11,225 leaking underground storage tank sites, 116 hazardous waste sites, and 415 reported spills and releases in Connecticut, among 20,870 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.
- 11,225
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 116
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 415
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 284
- lined landfills and transfer facilities
- 8,830
- other remediation projects
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
E. coli
Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
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
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 E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For E. coli
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
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
How deep are wells in Connecticut?
The typical domestic well in Connecticut is 350 feet deep, based on 3,681 wells reported to the state since 1925. One in ten is deeper than 600 feet.
Is there arsenic in well water in Connecticut?
Arsenic was detected in 22% of 1,099 public well samples in Connecticut, and 3% 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 Connecticut?
The median radon level across 96 public samples in Connecticut was 1,400 pCi/L, with a high of 650,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Connecticut?
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.
Planning regions in Connecticut
Want the numbers themselves? Download the Connecticut dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 15,118 samples in Connecticut. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Connecticut DPH and USGS arsenic and uranium survey: 1,235 samples in Connecticut. Arsenic and uranium in 674 private bedrock wells sampled by the Connecticut Department of Public Health with the U.S. Geological Survey, 2013 to 2015. Retrieved .
- Connecticut well completion reports: 7,992 well records in Connecticut, 3,681 domestic. Well completion reports filed online with the Connecticut Department of Consumer Protection since January 2021. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
- CT DEEP contaminated sites and landfills: 20,870 regulated sites located in Connecticut. Contaminated or potentially contaminated sites and solid waste landfills from the Connecticut Department of Energy and Environmental Protection. Retrieved September 16, 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.