Water Quality

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Drinking Water

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Drinking water quality in 2023 was very good, but chloride was again the most common contaminant detected in public water systems.


This indicator shows that 98.7 percent of the population served by community water systems (CWS) and 95.3 percent of all CWS demonstrated full compliance with applicable drinking water standards, based on an annual average. Data for 2023 also indicates that the percentage of the population served by CWS and the CWS were greater than the previous ten-year annual average of 98.5 percent and 93.9 percent, respectively.47  By far, the most common problem during 2023 in water systems was excessive levels of chloride, which is typical of most years.48 Source water protection is important for ensuring the safety and quantity of drinking water supplies.

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.49 Public Act 23-74 established an account to provide municipalities with grants or reimbursements to test for PFAS contamination in drinking water supplies and remediate any such contamination.

Over 80 percent of people in Connecticut are supplied by the public water systems, while 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 number of private wells are contaminated by pollution or naturally occurring toxins, such as arsenic and uranium. A 2020 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.50 The 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.

Goal: By 2018, 92 percent of community water systems will provide drinking water that meets all applicable health-based drinking water.51

Technical Note: *The vertical axis in the chart above has been shortened, beginning at 85 percent rather than the customary zero.  


47 EPA, Drinking Water Performance and Results Report, Government Performance and Results Act (GPRA) tool, GPRA Summary Report and GPRA Violation Report, accessed March 21, 2024; www.epa.gov/ground-water-and-drinking-water/drinking-water-performance-and-results-report.
Department of Public Health (DPH), Freedom of Information Response received February 15, 2023 and DPH, Public Water Systems Lists; portal.ct.gov/DPH/Drinking-Water/DWS/Public-Water-System-Lists.
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/Newsroom/Press-Releases---2022/PFAS-June-2022.
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.
EPA, FY2014 – FY2018 EPA Strategic Plan, Strategic Measures; www.epa.gov/ground-water-and-drinking-water/drinking-water-performance-and-results-report.