What was found in Norwalk'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 | 1339 µg/L 13% of the EPA limit 10000 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 2830 µg/L — AQUARION-DARIEN · 18,737 people · 2018 | 4/4 | SYR4 |
| Nitrate-Nitrite | 1285 µg/L 13% of the EPA limit 10000 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 2744.8 µg/L — AQUARION-DARIEN · 18,737 people · 2018 | 4/4 | SYR4 |
| Fluoride | 916 µg/L 23% of the EPA limit 4000 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 973 µg/L — SOUTH NORWALK ELECTRIC & WATER · 42,000 people · 2019 | 4/4 | SYR4 |
| Copper | 261 µg/L 20% of the EPA limit 1300 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 329.5 µg/L — AQUARION-DARIEN · 18,737 people · 2017 | 4/4 | SYR4 |
| TTHM | 80.7 µg/L 101% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 96.195 µg/L — SOUTH NORWALK ELECTRIC & WATER · 42,000 people · 2019 | 4/4 | SYR4 |
| Chloroform | 63 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 78.175 µg/L — SOUTH NORWALK ELECTRIC & WATER · 42,000 people · 2019 | 4/4 | SYR4 |
| Total Haloacetic Acids (HAA5) | 53.9 µg/L 90% of the EPA limit 60 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 4/4 | SYR4 |
| Barium | 48.9 µg/L 2.4% of the EPA limit 2000 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 51.9 µg/L — AQUARION-DARIEN · 18,737 people · 2015 | 4/4 | SYR4 |
| Lead | 42.65 µg/L 284% of the EPA limit, at the 95th percentile of samples — 15 µg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 4/4 | SYR4 |
| Trichloroacetic Acid | 29 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 3/4 | SYR4 |
| Dichloroacetic Acid | 24 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 3/4 | SYR4 |
| Bromodichloromethane | 16 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 4/4 | SYR4 |
| Dibromochloromethane | 3 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 6 µg/L — AQUARION-DARIEN · 18,737 people · 2019 | 4/4 | SYR4 |
| Gross Beta Particle Activity | 4.4 pCi/L No EPA limit set Highest in the city: NORWALK FIRST TAXING DISTRICT · 40,256 people · 2018 | 1/4 | SYR4 |
| Dibromoacetic Acid | 1 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 3.46 µg/L — SOUTH NORWALK ELECTRIC & WATER · 42,000 people · 2019 | 3/4 | SYR4 |
| Bromoform | 0.5950 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019
Highest in the city: 3 µg/L — AQUARION-DARIEN · 18,737 people · 2019 | 3/4 | SYR4 |
| Monochloroacetic Acid | 2 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 3/4 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 1.52 µg/L 25% of the EPA limit 6 µg/L Highest in the city: SOUTH NORWALK ELECTRIC & WATER · 42,000 people · 2019 | 1/4 | SYR4 |
| Monobromoacetic Acid | 1 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2019 | 2/4 | SYR4 |
| cis-1,2-Dichloroethylene | 0.7000 µg/L 1% of the EPA limit 70 µg/L Highest in the city: NORWALK FIRST TAXING DISTRICT · 40,256 people · 2019 | 1/4 | SYR4 |
| PFOS | 0.0066 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024
Highest in the city: 0.0112 µg/L — NORWALK FIRST TAXING DISTRICT · 40,256 people · 2024 | 2/4 | UCMR-5 |
| PFOA | 0.0109 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024 | 3/4 | UCMR-5 |
| Pfba | 0.0076 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024 | 2/4 | UCMR-5 |
| Pfhxa | 0.0074 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024 | 3/4 | UCMR-5 |
| Pfpea | 0.0067 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024 | 3/4 | UCMR-5 |
| PFBS | 0.0041 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024
Highest in the city: 0.0064 µg/L — NORWALK FIRST TAXING DISTRICT · 40,256 people · 2024 | 2/4 | UCMR-5 |
| PFHXS | 0.0042 µg/L No EPA limit set Highest in the city: NORWALK FIRST TAXING DISTRICT · 40,256 people · 2024 | 1/4 | UCMR-5 |
| Pfhpa | 0.0039 µg/L No EPA limit set Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2024 | 1/4 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: AQUARION-EASTERN FAIRFIELD COUNTY · 351,756 people · 2026
Highest in the city: 0.0030 mg/L — NORWALK FIRST TAXING DISTRICT · 40,256 people · 2025 | 4/4 | 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 Norwalk
| Supplier | Population served |
|---|---|
| AQUARION-EASTERN FAIRFIELD COUNTY | 351,756 |
| SOUTH NORWALK ELECTRIC & WATER | 42,000 |
| NORWALK FIRST TAXING DISTRICT | 40,256 |
| AQUARION-DARIEN | 18,737 |
Frequently asked questions about Norwalk tap water
Is Norwalk tap water safe to drink?
EPA testing detected 29 contaminants in the water serving Norwalk. 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 Norwalk?
4 public water suppliers report drinking-water monitoring for Norwalk, Connecticut to the EPA. Each is listed above with its population served.
What contaminants are in Norwalk's water?
The contaminants EPA monitoring detected in Norwalk 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.