Water Quality

Rivers, Lakes, and Estuaries                Water of Long Island Sound               Warming and Rising Waters               Swimming               Clamming and Oystering       

Drinking Water

This indicator shows that 99.8 percent of the time, the population served by Community Water systems and Non-Transient Non-Community Water systems demonstrated full compliance with applicable standards, after weighting the reports to account for the number of people served by each system over time. Data for 2022 show a slight increase in the number of violations, based on the number of people served, from 2021 levels.⁴⁰ By far, the most common problem during 2022 in water systems was excessive levels of chloride, which is typical of most years.

In June 2022, the Connecticut Department of Public Health (DPH) updated the “Drinking Water Action Level for Per And Polyfluoroalkyl Substances (PFAS) and renewed its recommendation to all public water systems to test the water delivered to their customers for PFAS.⁴¹

About 80 percent of people in Connecticut are supplied by the public water systems included in the chart above. The remainder of the population primarily relies on private wells, which are not monitored by any government agency and are not counted in this indicator. An unknown but potentially significant number of private wells are contaminated by pollution or naturally occurring toxins, such as arsenic and uranium. A recent United State Geological Survey study of groundwater samples collected from more than 2,000 private wells in bedrock aquifers in Connecticut found that 3.9 percent of collected samples contained arsenic concentrations greater than the U.S. Environmental Protection Agency’s (EPA) maximum contaminant level (MCL) of 10 micrograms per liter (µg/L), and 4.7 percent of collected samples contained uranium concentrations greater than the EPA MCL of 30 µg/L.⁴² he DPH provides guidelines for testing of private wells.

Public Act 22-58 made several changes affecting water quality testing for private and semipublic wells, including a requirement that property owners test the water quality of their newly constructed private or semipublic wells, and provide prospective homebuyers and renters with educational materials on well testing.

<sub>Goal: It is assumed that the goal is for everyone to have safe drinking water.

Technical Note: *The vertical axis in the chart above has been shortened, beginning at 97 percent rather than the customary zero. This allows the reader to see year-to-year differences, which would be nearly imperceptible if the chart began at zero. The chart above does not include “Transient Non-Community Systems”, that do not meet the definition of a non-transient, non-community water system such as restaurants, parks, etc.</sub> 

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⁴⁰ _{Department of Public Health (DPH), Freedom of Information Response dated April 4, 2023 and DPH, Public Water Systems Lists; portal.ct.gov/DPH/Drinking-Water/DWS/Public-Water-System-Lists.}
⁴¹ _{DPH, Press Releases, Connecticut Department of Public Health Updates Drinking Water Action Level For Per And Polyfluoroalkyl Substances (PFAS), June 15, 2022; portal.ct.gov/DPH/Press-Room/Press-Releases---2022/PFAS-June-2022.}
⁴² _{United States Geological Survey (USGS), “Arsenic and Uranium Occurrence in Private Wells in Connecticut, 2013–18— A Spatially Weighted and Bedrock Geology Assessment”; Eliza L. Gross and Craig J. Brown, Open-File Report 2021–1111. Version 1.1, November 2020. pubs.usgs.gov/of/2021/1111/ofr20211111.pdf.}