Well water in Connecticut: testing, risks and certified labs by county
About 23% of Connecticut residents get their drinking water from a private well. Private wells aren't covered by federal drinking water rules, so owners are responsible for testing their own water.
Source: CT DEEP Drinking Water FAQ
Counties
Fairfield County
Arsenic
About 11,400 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 7,700 to 16,800).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: High
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
3 certified private-well labs
Hartford County
Arsenic
About 3,600 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 2,400 to 5,300).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: Lower
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
2 certified private-well labs
Litchfield County
Arsenic
About 3,500 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 2,300 to 5,100).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: Moderate
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
No certified private-well labs are listed for Litchfield County.
Middlesex County
Arsenic
About 6,100 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 4,100 to 8,800).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: High
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
1 certified private-well lab
New Haven County
Arsenic
About 6,800 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 4,600 to 9,800).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: High
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
6 certified private-well labs
New London County
Arsenic
About 2,900 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 2,000 to 4,200).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: High
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
No certified private-well labs are listed for New London County.
Tolland County
Arsenic
About 12,100 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 8,700 to 16,700).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: Moderate
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
No certified private-well labs are listed for Tolland County.
Windham County
Arsenic
About 5,800 people on private wells may have arsenic above the drinking water limit of 10 micrograms per liter (likely 4,200 to 7,900).
USGS estimate based on 2010 population, published 2017.
Connecticut advises well owners to compare their results to this limit.
Radon
Indoor radon potential: Moderate
EPA zone for indoor air. It doesn't measure your well water.
Private-well labs
1 certified private-well lab
What to test for
The Connecticut Department of Public Health recommends these tests for every private well.
| Test | How often |
|---|---|
| Basic indicators (bacteria, nitrate, pH, iron and other common measures) | Every year, and after any repair to your well, pump or pipes, or if your well head floods |
| Arsenic, uranium and radon in water | At least once, ideally every 5 years |
| Lead | At least once; also if you're planning a pregnancy or have a child under 6; every 3 to 5 years if your water is corrosive |
| Volatile organic compounds (VOCs: gasoline, oil, solvents) | At least once; more often if a problem is suspected |
| Fluoride | Every 5 years when a child under 12 lives in the home |
Questions about testing or treatment? Call the CT DPH Private Well Program at (860) 509-8401.