Data Report

Connecticut Drinking Water Report 2026

By Alexander Snyder, Founder & Water Quality Data LeadPublished 2026-07-06

Reviewed against EPA · OEHHA · ATSDR & peer-reviewed science

CheckYourTap analyzed the most-detected drinking-water contaminants across 301 Connecticut ZIP codes spanning 221 towns and cities. The headline finding: lead is among the top detected contaminants in 266 of these ZIP codes and measures above its 0.015 mg/L federal action level in 198.

More broadly, 229 of the 301 ZIP codes (76%) have at least one contaminant among their top detections that exceeds a legal limit or health guideline. PFAS “forever chemicals” are widespread where tested: PFOA appears above its limit in 78 ZIP codes and PFOS in 73.

Key findings

Lead is the single most common concern. It appears among the top detections in 266 of 301 ZIP codes and exceeds its 0.015 mg/L action level in 198. Lead has no known safe level.
Most areas have at least one exceedance. 229 of 301 ZIP codes (76%) show one or more top-detected contaminants above a limit or health guideline.
PFAS are above the limit everywhere they surface. Where PFOA (78 ZIPs) and PFOS (73 ZIPs) appear in a ZIP's top detections, they exceed the 4 parts-per-trillion federal limit in every case.
Naturally occurring contaminants are common. Arsenic is a top detection 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 a top detection 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 301 covered ZIP codes in which each contaminant appears among that area's top detected substances. “Above a limit” counts ZIPs where the contaminant exceeds its legal limit or health guideline.

Contaminant	ZIPs where top-detected	ZIPs above a limit	What it is
Lead	266	198	Neurotoxic metal that leaches from older service lines and household plumbing. No level is considered safe, especially for children.
Copper	149	85	Leaches from copper pipes and brass fixtures. High levels can cause gastrointestinal distress.
Arsenic	142	20	Occurs naturally in New England bedrock and groundwater. A known carcinogen with chronic low-dose exposure.
Gross Beta	138	0	A screening measure of beta-emitting radioactivity from both natural and man-made sources.
Gross Alpha	128	0	A screening measure of alpha-emitting radioactivity from natural radionuclides (radium, uranium) in groundwater.
Barium	123	1	Naturally occurring metal from mineral deposits. Elevated levels are linked to blood-pressure effects.
Combined Radium 226/228	117	0	Naturally occurring radioactive elements common in New England groundwater and bedrock aquifers.
Nitrate	107	32	From fertilizer runoff and septic systems. Dangerous to infants under six months (blue-baby syndrome).
Cadmium	94	45	A toxic metal from pipe corrosion and industrial sources. Accumulates in and damages the kidneys.
Nitrate-Nitrite	85	24	Combined nitrogen compounds from agricultural and septic runoff, reported together.
chromium-6	82	0	Hexavalent chromium, an industrial contaminant and probable carcinogen studied in the 'Erin Brockovich' case.
PFOA	78	78	A PFAS 'forever chemical' linked to cancer and immune effects. The federal limit is 4 parts per trillion (2024).
PFOS	73	73	A PFAS 'forever chemical' with a 4-parts-per-trillion federal limit set in 2024.
DEHP (Phthalate)	72	22	A plastic-softening chemical that can leach from materials in contact with water. A probable human carcinogen.
HAA9	71	71	A group of nine haloacetic-acid disinfection byproducts formed when chlorine reacts with organic matter.

Data snapshot: 2026-07-04. Counts reflect the top detected contaminants recorded for each ZIP code, not a full analyte panel.

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.

That is why we compare every result against the strictest applicable health guideline alongside the legal limit. The goal is not to alarm—it is to give Connecticut families the same information a toxicologist would use.

How we measured this

This report aggregates the top detected contaminants for each of 301 Connecticut ZIP codes (covering 221 towns and cities) from CheckYourTap's water-quality database, built from three public sources: EPA SDWIS (federal compliance testing), USGS NWIS (groundwater monitoring), and the EWG Tap Water Database (health-guideline comparisons).

Important scope note

Our per-ZIP records capture each area's most-detected contaminants—not a complete analyte panel. Every statewide figure here should be read as “among the most-detected contaminants in each ZIP” across the 301 ZIP codes we cover. These numbers do not describe all Connecticut water, and a contaminant not shown for an area may simply not be in that area's top detections or may lack testing data. “Above a limit” means a measured exceedance greater than zero against the contaminant's legal limit or health guideline.

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 for a free, personalized report on the contaminants detected where you live.

Check My Water

Health 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.