Data Report
Connecticut Drinking Water Report 2026
CheckYourTap analyzed the most-detected drinking-water contaminants across 300 Connecticut ZIP codes spanning 226 place names. The headline finding: lead is among the top detected contaminants in 265 of these ZIP codes, and in 197 of them at least one sample in the record measured above 0.015 mg/L.
That is not the same as exceeding the federal lead action level. The preserved artifact does not carry the source-row and denominator fields needed to reproduce a water system’s 90th-percentile Lead and Copper Rule determination. The historical occurrence count remains visible, but no ZIP is labeled an action-level exceedance from this artifact.
More broadly, 228 of the 300 ZIP codes (76%) retain at least one row marked above the comparator stored in the historical artifact. That is not a present-condition or compliance rate. PFAS “forever chemicals” are widespread where tested: PFOA appears above its limit in 78 ZIP codes and PFOS in 73.
Read that figure carefully, because we would rather you heard its limits from us. “At least one contaminant, ever, above a limit” is a low bar: it means a single sample, at any point in a record that reaches back to 2006. It is not a statement that the water is currently over a limit, and it is not a share of samples. It also cannot be one, because most of our city-water source drops non-detects at ingest, so for those contaminants the clean samples are simply not in the denominator. (Lead, PFAS, chromium-6 and a handful of others are the exceptions: those programmes do report their non-detects, so their percentages are real and are over all samples tested. We decide that per row, from the data, rather than from a list.) So we only publish a detection rate where the data can actually support one: where the source reported its non-detects, we give the rate and name the denominator, and where it did not, we say the contaminant was detected and give no percentage at all. We removed the old blanket figure in July 2026, once we realised it was reading 100% on three quarters of our rows. We sell water treatment, so a statistic that inflates in our favour is one we have to be especially hard on.
Key findings
- Lead is the single most common concern. It appears in the reported record for 265 of 300 ZIP codes, and at least one sample measured above 0.015 mg/L in 197. That is not the same as exceeding the action level, which is a water-system, monitoring-period, 90th-percentile test. The preserved artifact cannot reproduce that determination, so no action-level count is inferred. Lead has no known safe level.
- Most areas have at least one exceedance. 228 of 300 ZIP codes (76%) retain one or more rows marked above their stored comparator. In the historical artifact this is an occurrence count, not a current compliance or safety verdict.
- PFAS exceedances are explicitly counted where tested. PFOA has recorded exceedances in 78 ZIPs and PFOS in 73. Those are ZIP-level occurrence counts, not claims that every current sample exceeds.
- Naturally occurring contaminants are common. Arsenic is reported in 142 ZIPs (above its limit in 20), and radiological screening measures (Gross Alpha, Combined Radium 226/228) rank among the most frequent, reflecting New England bedrock geology.
- Nitrate and copper round out the pipe-and-runoff risks. Copper is reported in 149 ZIPs (above its limit in 85); nitrate appears in 107 (above its limit in 32).
Most common contaminants across Connecticut
Ranked by the number of the 300 covered ZIP codes in which each contaminant appears in the preserved historical ZIP-associated artifact. “Above a comparator” counts ZIPs with a retained positive comparator flag; it is not a property, current-condition, or compliance finding.
| Contaminant | ZIPs where reported | ZIPs above comparator |
|---|---|---|
| Lead | 265 | 197 |
| Copper | 149 | 85 |
| Arsenic | 142 | 20 |
| Gross Beta | 137 | 0 |
| Gross Alpha | 129 | 0 |
| Barium | 122 | 1 |
| Combined Radium 226/228 | 116 | 0 |
| Nitrate | 107 | 32 |
| Cadmium | 95 | 45 |
| Nitrate-Nitrite | 85 | 24 |
| chromium-6 | 81 | 0 |
| PFOA | 78 | 78 |
| PFOS | 73 | 73 |
| DEHP (Phthalate) | 72 | 22 |
| HAA5 | 63 | 63 |
Page rebuilt: 2026-08-10. Sample-year coverage: 2006–2027. Data state: preserved historical ZIP-associated artifact; current release pending. The visible table is a ranked summary.
Healthy, not just legal
A water system can be fully compliant with federal law and still deliver water that health scientists would flag. Legal limits are decades old for many contaminants and were set with cost and feasibility in mind—not purely health. For several substances in this report, including lead, arsenic, and PFAS, the health-protective guideline is far below the enforceable limit, and for lead there is no level considered safe at all.
The ranked statistics above do not make that health comparison. They use the comparator exported with each row: an enforceable legal limit where one is established, otherwise an explicitly non-enforceable reference or secondary standard. ZIP-record reports present governed reference context separately so the two frames cannot be mistaken for one another.
How we measured this
This report aggregates the preserved historical ZIP-associated record artifact for each of 300 Connecticut ZIP codes (covering 226 place names, across Connecticut's 169 legal towns) from CheckYourTap's water-quality database. It is not a complete historical contaminant inventory. It is built from public compliance and monitoring sources: EPA SDWIS (federal compliance testing) and the Connecticut Department of Public Health drinking-water program (state public-water oversight and records).
Important scope note
Our per-ZIP artifact contains every retained contaminant row in its stated release scope, but it is not proof that every possible analyte was tested in every system. These numbers do not describe all Connecticut water, and a contaminant not shown for an area may lack testing data or a usable source mapping. “Above a comparator” means at least one recorded exceedance against the row's enforceable legal limit or clearly labeled non-enforceable reference standard.
For the full data pipeline—source reconciliation, unit harmonization, and health-guideline logic—see our methodology page.
What's in your ZIP code?
Statewide numbers only go so far. Enter your ZIP to review available public-system records or regional groundwater context associated with the area.
Check My WaterHealth disclaimer: This report is general information, not medical advice or a substitute for certified laboratory testing. Contaminant levels can vary between neighboring homes due to plumbing and local conditions. Talk to your pediatrician or physician about specific health concerns, and consult a certified lab for a definitive test of your own water.