What was found in Madison's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate | 2782 µg/L 28% of the EPA limit 10000 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 5292.5 µg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 3/3 | SYR4 |
| Nitrate-Nitrite | 2755 µg/L 28% of the EPA limit 10000 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 5056 µg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 3/3 | SYR4 |
| Fluoride | 1037 µg/L 26% of the EPA limit 4000 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 3/3 | SYR4 |
| Copper | 325.55 µg/L 25% of the EPA limit 1300 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 500.6 µg/L — CTWC - LEGEND HILL SYSTEM · 1,368 people · 2019 | 3/3 | SYR4 |
| TTHM | 51.795 µg/L 65% of the EPA limit 80 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Barium | 21.95 µg/L 1.1% of the EPA limit 2000 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 46.65 µg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 3/3 | SYR4 |
| Chloroform | 35 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Total Haloacetic Acids (HAA5) | 29.25 µg/L 49% of the EPA limit 60 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Lead | 4.54 µg/L 30% of the EPA limit 15 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 24.3 µg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 3/3 | SYR4 |
| Gross Beta Particle Activity | 23.194 pCi/L No EPA limit set Highest in the city: CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 1/3 | SYR4 |
| Trichloroacetic Acid | 16 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 1/3 | SYR4 |
| Dichloroacetic Acid | 13.25 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Bromodichloromethane | 11.08 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Gross Alpha, Excl. Radon And U | 2.1 pCi/L 14% of the EPA limit 15 pCi/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 7.3565 pCi/L — CTWC - LEGEND HILL SYSTEM · 1,368 people · 2019 | 3/3 | SYR4 |
| Combined Uranium | 1.05 µg/L 3.5% of the EPA limit 30 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 5.8955 µg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2019 | 2/3 | SYR4 |
| Nitrite | 5.85 µg/L 0.6% of the EPA limit 1000 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 2 µg/L 33% of the EPA limit 6 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 3.47 µg/L — CTWC - LEGEND HILL SYSTEM · 1,368 people · 2019 | 2/3 | SYR4 |
| Dibromochloromethane | 3.2 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Monochloroacetic Acid | 3.08 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 1/3 | SYR4 |
| Combined Radium (-226 And -228) | 2.614 pCi/L 52% of the EPA limit 5 pCi/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 2.678 pCi/L — CTWC - LEGEND HILL SYSTEM · 1,368 people · 2019 | 2/3 | SYR4 |
| Dibromoacetic Acid | 2.3 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 2/3 | SYR4 |
| Bromoform | 0.6235 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019
Highest in the city: 0.9250 µg/L — CTWC - LEGEND HILL SYSTEM · 1,368 people · 2019 | 2/3 | SYR4 |
| Arsenic | 0.7000 µg/L 7% of the EPA limit 10 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 1/3 | SYR4 |
| Beryllium, Total | 0.4000 µg/L 10% of the EPA limit 4 µg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2019 | 1/3 | SYR4 |
| Pfba | 0.0120 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| PFOS | 0.0120 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| PFOA | 0.0060 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| PFBS | 0.0050 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| Pfhxa | 0.0040 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| PFHXS | 0.0040 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| Pfpea | 0.0040 µg/L No EPA limit set Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2025 | 1/3 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: CTWC - SHORELINE REGION-GUILFORD SYSTEM · 33,975 people · 2026
Highest in the city: 0.0033 mg/L — CTWC - GREEN SPRINGS SYSTEM · 104 people · 2025 | 3/3 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Madison
| Supplier | Population served |
|---|---|
| CTWC - SHORELINE REGION-GUILFORD SYSTEM | 33,975 |
| CTWC - LEGEND HILL SYSTEM | 1,368 |
| CTWC - GREEN SPRINGS SYSTEM | 104 |
Frequently asked questions about Madison tap water
Is Madison tap water safe to drink?
EPA testing detected 32 contaminants in the water serving Madison. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Madison?
3 public water suppliers report drinking-water monitoring for Madison, Connecticut to the EPA. Each is listed above with its population served.
What contaminants are in Madison's water?
The contaminants EPA monitoring detected in Madison include Nitrate, Nitrate-Nitrite, Fluoride, Copper, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.