What was found in Barnstable'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 | 4940 µg/L 49% of the EPA limit 10000 µg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2019
Highest in the city: 5000 µg/L — HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 4/4 | SYR4 |
| Copper | 27.25 µg/L 2.1% of the EPA limit 1300 µg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2017
Highest in the city: 591.05 µg/L — HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 4/4 | SYR4 |
| Nitrite | 440 µg/L 44% of the EPA limit 1000 µg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2017 | 1/4 | SYR4 |
| Fluoride | 100 µg/L 2.5% of the EPA limit 4000 µg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2017 | 2/4 | SYR4 |
| Barium | 69.3 µg/L 3.5% of the EPA limit 2000 µg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2017
Highest in the city: 93.8 µg/L — HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 4/4 | SYR4 |
| TTHM | 18 µg/L 23% of the EPA limit 80 µg/L Highest in the city: BARNSTABLE FIRE DISTRICT · 5,400 people · 2019 | 3/4 | SYR4 |
| Dibromochloromethane | 6.6 µg/L No EPA limit set Highest in the city: BARNSTABLE FIRE DISTRICT · 5,400 people · 2019 | 3/4 | SYR4 |
| Bromoform | 5.57 µg/L No EPA limit set Highest in the city: BARNSTABLE FIRE DISTRICT · 5,400 people · 2019 | 3/4 | SYR4 |
| Bromodichloromethane | 4.725 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Total Haloacetic Acids (HAA5) | 4.62 µg/L 7.7% of the EPA limit 60 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Monochloroacetic Acid | 4.06 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 2/4 | SYR4 |
| Selenium | 4 µg/L 8% of the EPA limit 50 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Chloroform | 3.9 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Monobromoacetic Acid | 3.9 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Arsenic | 3.55 µg/L 36% of the EPA limit 10 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Dibromoacetic Acid | 2.35 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Tetrachloroethylene | 2.2 µg/L 44% of the EPA limit 5 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Dichloroacetic Acid | 2.151 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 2/4 | SYR4 |
| cis-1,2-Dichloroethylene | 2 µg/L 2.9% of the EPA limit 70 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Trichloroacetic Acid | 1.78 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 3/4 | SYR4 |
| Trichloroethylene | 0.6500 µg/L 13% of the EPA limit 5 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Cadmium | 0.2085 µg/L 4.2% of the EPA limit 5 µg/L Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2019 | 1/4 | SYR4 |
| Pfpea | 0.0075 µg/L No EPA limit set Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025
Highest in the city: 0.0298 µg/L — HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2024 | 3/4 | UCMR-5 |
| PFBS | 0.0040 µg/L No EPA limit set Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025
Highest in the city: 0.0182 µg/L — BARNSTABLE FIRE DISTRICT · 5,400 people · 2023 | 2/4 | UCMR-5 |
| Pfba | 0.0168 µg/L No EPA limit set Highest in the city: HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE · 35,000 people · 2024 | 1/4 | UCMR-5 |
| PFOS | 0.0071 µg/L No EPA limit set Highest in the city: BARNSTABLE FIRE DISTRICT · 5,400 people · 2023 | 1/4 | UCMR-5 |
| Pfhxa | 0.0069 µg/L No EPA limit set Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025 | 3/4 | UCMR-5 |
| PFOA | 0.0049 µg/L No EPA limit set Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025 | 2/4 | UCMR-5 |
| PFHXS | 0.0031 µg/L No EPA limit set Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025
Highest in the city: 0.0036 µg/L — BARNSTABLE FIRE DISTRICT · 5,400 people · 2023 | 2/4 | UCMR-5 |
| Lead | 0.0024 mg/L 16% of the EPA limit 0.0150 mg/L Main supplier: CENTERVILLE OSTERVILLE MARSTONS MILLS WD · 50,000 people · 2025
Highest in the city: 0.0031 mg/L — COTUIT FIRE DISTRICT WATER DEPARTMENT · 4,938 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 Barnstable
| Supplier | Population served |
|---|---|
| CENTERVILLE OSTERVILLE MARSTONS MILLS WD | 50,000 |
| HYANNIS WATER SYSTEM, TOWN OF BARNSTABLE | 35,000 |
| BARNSTABLE FIRE DISTRICT | 5,400 |
| COTUIT FIRE DISTRICT WATER DEPARTMENT | 4,938 |
Frequently asked questions about Barnstable tap water
Is Barnstable tap water safe to drink?
EPA testing detected 30 contaminants in the water serving Barnstable. 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 Barnstable?
4 public water suppliers report drinking-water monitoring for Barnstable, Massachusetts to the EPA. Each is listed above with its population served.
What contaminants are in Barnstable's water?
The contaminants EPA monitoring detected in Barnstable include Nitrate, Copper, Nitrite, Fluoride, Barium. 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.