What was found in Sonoma'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 | 1700 µg/L 17% of the EPA limit 10000 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 3/5 | SYR4 |
| Fluoride | 448 µg/L 11% of the EPA limit 4000 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 581 µg/L — MOON VALLEY WATER SYSTEM · 691 people · 2019 | 4/5 | SYR4 |
| Lithium | 40 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2024 | 1/5 | UCMR-5 |
| TTHM | 31.549999999999997 µg/L 39% of the EPA limit 80 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 3/5 | SYR4 |
| Barium | 25.779999999999998 µg/L 1.3% of the EPA limit 2000 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 1/5 | SYR4 |
| Total Haloacetic Acids (HAA5) | 7.139999999999998 µg/L 12% of the EPA limit 60 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 17.46 µg/L — DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 3/5 | SYR4 |
| Chloroform | 14.099999999999994 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 2/5 | SYR4 |
| Bromodichloromethane | 10 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 3/5 | SYR4 |
| Arsenic | 8.3 µg/L 83% of the EPA limit 10 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 9.405 µg/L — MOON VALLEY WATER SYSTEM · 691 people · 2019 | 4/5 | SYR4 |
| Dibromochloromethane | 8.279999999999996 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 3/5 | SYR4 |
| Dichloroacetic Acid | 4.039999999999999 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 5.618 µg/L — DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 2/5 | SYR4 |
| Monochloroacetic Acid | 4.68 µg/L No EPA limit set Highest in the city: DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 1/5 | SYR4 |
| Dibromoacetic Acid | 1.7799999999999996 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 4.1514999999999995 µg/L — DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 3/5 | SYR4 |
| Monobromoacetic Acid | 3.57 µg/L No EPA limit set Highest in the city: DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 1/5 | SYR4 |
| Trichloroacetic Acid | 2.17 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 2/5 | SYR4 |
| Bromoform | 2.0299999999999994 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2019
Highest in the city: 2.1 µg/L — DIAMOND A MUTUAL WATER COMPANY · 640 people · 2017 | 3/5 | SYR4 |
| Chromium | 0.9790 µg/L 1% of the EPA limit 100 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2019 | 1/5 | SYR4 |
| Lead | 0.2900 µg/L 1.9% of the EPA limit 15 µg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2016 | 1/5 | SYR4 |
| PFOA | 0.0062 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2024 | 1/5 | UCMR-5 |
| Pfhxa | 0.0061 µg/L No EPA limit set Main supplier: SONOMA, CITY OF · 11,725 people · 2024 | 1/5 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: SONOMA, CITY OF · 11,725 people · 2023 | 4/5 | 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 Sonoma
| Supplier | Population served |
|---|---|
| SONOMA, CITY OF | 11,725 |
| MOON VALLEY WATER SYSTEM | 691 |
| DIAMOND A MUTUAL WATER COMPANY | 640 |
| MISSION HIGHLANDS MUTUAL WATER CO. | 150 |
| EDDY DRIVE | 48 |
Frequently asked questions about Sonoma tap water
Is Sonoma tap water safe to drink?
EPA testing detected 21 contaminants in the water serving Sonoma. 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 Sonoma?
5 public water suppliers report drinking-water monitoring for Sonoma, California to the EPA. Each is listed above with its population served.
What contaminants are in Sonoma's water?
The contaminants EPA monitoring detected in Sonoma include Nitrate, Fluoride, Lithium, TTHM, 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.