Systems with a yearly average at or above an EPA-based study benchmark
45.9%28 of 61 active community water systems
All 61 systems had enough required samples to calculate a yearly average. 28 had at least one yearly average at or above a study benchmark; 33 did not.
EPA-based study benchmark: the unrounded cutoff this research uses to reproduce EPA’s January 2026 technical-assistance classification around the April 2024 federal levels. It is not a current standard or compliance finding and cannot determine household exposure or health risk.
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Find your water system
ZIP codes are used only to route visitors to public water systems that reported serving them. Confirm the actual provider using a water bill or utility record.
Compound summary
System counts in Connecticut
Each count shows how many included water systems had a yearly average at or above the named study benchmark.
| Study benchmark | Systems at or above benchmark | Water systems included | Percent |
|---|---|---|---|
| PFOA: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 25 | 61 | 41.0% |
| PFOS: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 20 | 61 | 32.8% |
| PFHxS: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 61 | 0.0% |
| PFNA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 61 | 0.0% |
| HFPO-DA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 61 | 0.0% |
| Hazard Index: 1.5 study benchmark with at least two detected components (reproduces EPA classification around 1) | 0 | 61 | 0.0% |
System directory
Community water systems with complete monitoring
“Complete monitoring” means at least one sampling location had all required samples needed for a yearly average. Each PWSID appears once, preventing double counting across ZIP associations.
| Public water system | PWSID | Population served | Primary source | Sampling locations | Study benchmark result |
|---|---|---|---|---|---|
| AQUARION WATER CO OF CT-GREENWICH SYSTEM | CT0570011 | 53,297 | Surface water | 3 | At or above a study benchmark |
| AQUARION WATER CO OF CT-LITCHFIELD SYS | CT0740011 | 3,097 | Surface water purchased | 3 | Below all study benchmarks |
| AQUARION WATER CO OF CT-MAIN SYSTEM | CT0150011 | 351,756 | Surface water | 5 | Below all study benchmarks |
| AQUARION WATER CO OF CT-MYSTIC | CT1370011 | 10,788 | Surface water | 2 | Below all study benchmarks |
| AQUARION WATER CO OF CT-NEW CANAAN SYS | CT0900011 | 10,097 | Surface water purchased | 1 | Below all study benchmarks |
| AQUARION WATER CO OF CT-NEW MILFORD | CT0960011 | 13,331 | Ground water | 5 | At or above a study benchmark |
| AQUARION WATER CO OF CT-NEWTOWN SYSTEM | CT0970011 | 6,054 | Ground water | 2 | At or above a study benchmark |
| AQUARION WATER CO OF CT-NOROTON SYSTEM | CT0350011 | 18,737 | Surface water purchased | 2 | Below all study benchmarks |
| AQUARION WATER CO OF CT-RIDGEFIELD SYS | CT1180011 | 7,476 | Surface water purchased | 4 | At or above a study benchmark |
| AQUARION WATER CO OF CT-SIMSBURY SYSTEM | CT1280021 | 14,691 | Ground water | 3 | Below all study benchmarks |
| AQUARION WATER CO OF CT-STAMFORD | CT1350011 | 119,214 | Surface water | 2 | Below all study benchmarks |
| AQUARION WATER CO OF CT-TLWC WOODRICH | CT1666011 | 72 | Ground water | 1 | At or above a study benchmark |
| AQUARION WATER CO OF CT-VALLEY SYSTEM | CT1240011 | 13,080 | Surface water purchased | 4 | At or above a study benchmark |
| Avon Water Co. | CT0040011 | 11,590 | Ground water | 6 | At or above a study benchmark |
| BERLIN WATER CONTROL COMMISSION | CT0070021 | 5,128 | Surface water purchased | 3 | Below all study benchmarks |
| BETHEL WATER DEPT | CT0090011 | 9,507 | Surface water | 1 | At or above a study benchmark |
| BRISTOL WATER DEPARTMENT | CT0170011 | 52,079 | Surface water | 4 | At or above a study benchmark |
| COLCHESTER SEWER & WATER COMMISSION | CT0280011 | 4,020 | Ground water | 4 | At or above a study benchmark |
| CROMWELL FIRE DISTRICT WATER DEPARTMENT | CT0330011 | 14,316 | Ground water | 1 | Below all study benchmarks |
| CTWC - COVENTRY HILLS DIV | CT0320091 | 700 | Ground water | 1 | Below all study benchmarks |
| CTWC - CRYSTAL SYSTEM | CT0690011 | 6,378 | Ground water | 2 | At or above a study benchmark |
| CTWC - NAUGATUCK REG-COLLINSVILLE SYS | CT0230011 | 6,324 | Surface water | 2 | At or above a study benchmark |
| CTWC - NAUGATUCK REG-TERRYVILLE SYSTEM | CT1110011 | 5,607 | Ground water | 2 | Below all study benchmarks |
| CTWC - NAUGATUCK REG-THOMASTON SYSTEM | CT1400011 | 3,789 | Ground water | 1 | Below all study benchmarks |
| CTWC - NAUGATUCK REGION-CENTRAL SYSTEM | CT0880011 | 22,735 | Surface water | 1 | Below all study benchmarks |
| CTWC - NORTHERN REG-WESTERN SYSTEM | CT0473011 | 101,313 | Surface water | 7 | At or above a study benchmark |
| CTWC - SHORELINE REGION-CHESTER SYSTEM | CT0261031 | 5,030 | Surface water | 2 | Below all study benchmarks |
| CTWC - SHORELINE REGION-GUILFORD SYSTEM | CT0608011 | 33,975 | Surface water | 10 | At or above a study benchmark |
| CTWC - UNIONVILLE SYSTEM | CT0520011 | 14,693 | Surface water purchased | 4 | At or above a study benchmark |
| DANBURY WATER DEPARTMENT | CT0340011 | 62,055 | Surface water | 2 | At or above a study benchmark |
| EAST LYME WATER & SEWER COMMISSION | CT0450011 | 15,245 | Surface water purchased | 6 | At or above a study benchmark |
| GROTON UTILITIES | CT0590011 | 30,200 | Surface water | 1 | Below all study benchmarks |
| HAZARDVILLE WATER COMPANY | CT0490021 | 18,544 | Ground water | 6 | At or above a study benchmark |
| HERITAGE WATER COMPANY | CT1300021 | 7,300 | Surface water purchased | 2 | Below all study benchmarks |
| JEWETT CITY WATER COMPANY | CT0580011 | 6,840 | Surface water | 2 | Below all study benchmarks |
| KENSINGTON FIRE DISTRICT | CT0070011 | 7,553 | Surface water purchased | 2 | Below all study benchmarks |
| MANCHESTER WATER DEPARTMENT | CT0770021 | 51,198 | Surface water | 7 | At or above a study benchmark |
| MERIDEN WATER DIVISION | CT0800011 | 58,441 | Surface water | 7 | At or above a study benchmark |
| METROPOLITAN DISTRICT COMMISSION | CT0640011 | 390,887 | Surface water | 3 | Below all study benchmarks |
| MIDDLETOWN WATER DEPARTMENT | CT0830011 | 41,019 | Surface water | 2 | Below all study benchmarks |
| Mashantucket Pequot Water System | 010106001 | 22,171 | Groundwater under influence of surface water | 1 | At or above a study benchmark |
| Mohegan Tribal Utility Authority | 010109005 | 31,961 | Surface water purchased | 1 | Below all study benchmarks |
| NEW BRITAIN WATER DEPARTMENT | CT0890011 | 73,534 | Surface water | 1 | Below all study benchmarks |
| NEW HARTFORD WATER DEPARTMENT | CT0920011 | 1,872 | Ground water | 2 | Below all study benchmarks |
| NEW LONDON DEPT. OF PUBLIC UTILITIES | CT0950011 | 27,620 | Surface water | 1 | Below all study benchmarks |
| NORWALK FIRST TAXING DISTRICT | CT1030011 | 40,256 | Surface water | 2 | At or above a study benchmark |
| NORWICH PUBLIC UTILITIES | CT1040011 | 36,163 | Surface water | 3 | At or above a study benchmark |
| PORTLAND WATER DEPARTMENT | CT1130011 | 5,010 | Surface water purchased | 1 | Below all study benchmarks |
| PUTNAM WATER POLLUTION CONTROL AUTHORITY | CT1160011 | 7,300 | Surface water | 3 | At or above a study benchmark |
| REGIONAL WATER AUTHORITY | CT0930011 | 418,900 | Surface water | 11 | At or above a study benchmark |
| SOUTH NORWALK ELECTRIC & WATER | CT1030021 | 42,000 | Surface water | 1 | Below all study benchmarks |
| SOUTHINGTON WATER DEPARTMENT | CT1310011 | 43,069 | Surface water | 7 | At or above a study benchmark |
| TORRINGTON WATER COMPANY | CT1430011 | 37,915 | Surface water | 1 | Below all study benchmarks |
| UNIVERSITY OF CONNECTICUT - MAIN CAMPUS | CT0780021 | 27,199 | Surface water purchased | 2 | At or above a study benchmark |
| VALLEY WATER SYSTEMS, INC. | CT1100011 | 18,231 | Ground water | 2 | At or above a study benchmark |
| WATERBURY WATER DEPARTMENT | CT1510011 | 107,271 | Surface water | 1 | Below all study benchmarks |
| WATERFORD WPCA | CT1520071 | 16,578 | Surface water purchased | 1 | Below all study benchmarks |
| WATERTOWN FIRE DISTRICT | CT1530011 | 6,718 | Ground water | 1 | Below all study benchmarks |
| WATERTOWN WATER & SEWER AUTHORITY | CT1530021 | 9,972 | Surface water purchased | 1 | Below all study benchmarks |
| WINDHAM WATER WORKS | CT1630011 | 21,214 | Surface water | 1 | Below all study benchmarks |
| WINSTED WATER WORKS | CT1620011 | 7,784 | Surface water | 1 | Below all study benchmarks |
How the count works
What is included
Each active community water system with enough required samples for a yearly average is counted once, even if it is linked with several ZIP codes. This does not mean every home was tested. Private wells are excluded, and UCMR 5 did not comprehensively monitor every small system. This page does not apply Connecticut's state-specific standards or determine compliance. Use the official state or territory drinking-water program for current regulatory information.