63 public water systems in Connecticut were sampled in EPA's UCMR 5 programme (2023–2025); we show six PFAS and lithium. Read 2026-10-31.
35 of 63 systems had at least one sample above a 2024 federal limit; 37 had at least one PFAS found above the reporting level; 26 had none found above the reporting level.
A single sample above a 2024 limit is a measurement, not a violation. Compliance is judged on running yearly averages, and water systems have until 2029 to meet the limits. On 20 May 2026 EPA proposed giving qualifying systems until 2031 for PFOA and PFOS and removing the limits for PFHxS, PFNA and HFPO-DA; those proposals were not final when we last checked (5 Nov 2026). Counts are per system, not per person; population figures are available only for systems serving more than 25,000 people (about 2,236,628 people across those systems here). UCMR 5 was a one-time national monitoring programme (2023–2025). The results are a snapshot at the system's entry points or taps on the sample dates, not a continuous measurement and not a compliance record.
| System | People served | UCMR 5 result |
|---|---|---|
| Regional Water Authority Regional Water Authority | 418,900 | Above the 2024 limit in at least one sample |
| Metropolitan District Commission Metropolitan District Commission | 390,887 | None detected (below the reporting level) |
| Aquarion Water Co of Connecticut, Main System Aquarion Water Co of Ct-Main System | 351,756 | Above the 2024 limit in at least one sample |
Pages for these are being added in stages. The data for all 63 systems is in the public dataset.
| System | People served | UCMR 5 result |
|---|---|---|
| Aquarion Water Co of Ct-Stamford Aquarion Water Co of Ct-Stamford | 119,214 | Above the 2024 limit in at least one sample |
| Waterbury Water Department Waterbury Water Department | 107,271 | None detected (below the reporting level) |
| Ctwc - Northern Reg-Western System Ctwc - Northern Reg-Western System | 101,313 | Above the 2024 limit in at least one sample |
| New Britain Water Department New Britain Water Department | 73,534 | None detected (below the reporting level) |
| Danbury Water Department Danbury Water Department | 62,055 | Above the 2024 limit in at least one sample |
| Meriden Water Division Meriden Water Division | 58,441 | Above the 2024 limit in at least one sample |
| Aquarion Water Co of Ct-Greenwich System Aquarion Water Co of Ct-Greenwich System | 53,297 | Above the 2024 limit in at least one sample |
| Bristol Water Department Bristol Water Department | 52,079 | Above the 2024 limit in at least one sample |
| Manchester Water Department Manchester Water Department | 51,198 | Above the 2024 limit in at least one sample |
| Southington Water Department Southington Water Department | 43,069 | Above the 2024 limit in at least one sample |
| South Norwalk Electric & Water South Norwalk Electric & Water | 42,000 | None detected (below the reporting level) |
| Middletown Water Department Middletown Water Department | 41,019 | None detected (below the reporting level) |
| Norwalk First Taxing District Norwalk First Taxing District | 40,256 | Above the 2024 limit in at least one sample |
| Torrington Water Company Torrington Water Company | 37,915 | None detected (below the reporting level) |
| Wallingford Water Department Wallingford Water Department | 37,267 | Above the 2024 limit in at least one sample |
| Norwich Public Utilities Norwich Public Utilities | 36,163 | Above the 2024 limit in at least one sample |
| Ctwc - Shoreline Region-Guilford System Ctwc - Shoreline Region-Guilford System | 33,975 | Above the 2024 limit in at least one sample |
| Groton Utilities Groton Utilities | 30,200 | None detected (below the reporting level) |
| New London Dept. of Public Utilities New London Dept. of Public Utilities | 27,620 | None detected (below the reporting level) |
| University of Connecticut - Main Campus University of Connecticut - Main Campus | 27,199 | Above the 2024 limit in at least one sample |
| Avon Water Co. Avon Water Co. | — | Above the 2024 limit in at least one sample |
| Sterling Engineering Corp. Sterling Engineering Corp. | — | None detected (below the reporting level) |
| Kensington Fire District Kensington Fire District | — | None detected (below the reporting level) |
| Berlin Water Control Commission Berlin Water Control Commission | — | Detected, below the 2024 limit |
| Bethel Water Dept Bethel Water Dept | — | Above the 2024 limit in at least one sample |