What was found in San Luis Obispo'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-Nitrite | 200000 µg/L 2000% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 840000 µg/L — SANTA YSABEL RANCH MWC · 344 people · 2017 | 13/20 | SYR4 |
| Nitrate | 4300 µg/L 43% of the EPA limit 10000 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 500000 µg/L — CALIFORNIA MENS COLONY · 15,000 people · 2019 | 15/20 | SYR4 |
| Fluoride | 800 µg/L 20% of the EPA limit 4000 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 1505 µg/L — AFUERA DE CHORRO WATER COMPANY · 85 people · 2018 | 18/20 | SYR4 |
| Barium | 159.3 µg/L 8% of the EPA limit 2000 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 368.5 µg/L — HIGUERA APARTMENTS · 30 people · 2017 | 16/20 | SYR4 |
| Copper | 203 µg/L 16% of the EPA limit 1300 µg/L Highest in the city: LOPEZ PROJECT · 1,569 people · 2019 | 4/20 | SYR4 |
| Cyanide | 197.5 µg/L 99% of the EPA limit 200 µg/L Highest in the city: CALLENDER GROVE MUTUAL WATER · 126 people · 2018 | 1/20 | SYR4 |
| TTHM | 91.8 µg/L 115% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 109.5 µg/L — MONTE SERENO MUTUAL BENEFIT WATER · 65 people · 2019 | 12/20 | SYR4 |
| Chloroform | 59.3 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019 | 11/20 | SYR4 |
| Lead | 7.185 µg/L 48% of the EPA limit 15 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 54.61 µg/L — BEAR VALLEY WATER COMPANY · 45 people · 2019 | 6/20 | SYR4 |
| Total Haloacetic Acids (HAA5) | 43.85 µg/L 73% of the EPA limit 60 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 49.98 µg/L — LOPEZ PROJECT · 1,569 people · 2019 | 11/20 | SYR4 |
| Dibromochloromethane | 16.875 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 45.65 µg/L — MONTE SERENO MUTUAL BENEFIT WATER · 65 people · 2019 | 12/20 | SYR4 |
| Bromodichloromethane | 22.86 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 33.9 µg/L — MONTE SERENO MUTUAL BENEFIT WATER · 65 people · 2019 | 12/20 | SYR4 |
| Selenium | 3 µg/L 6% of the EPA limit 50 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 33.6 µg/L — SLO CSA NO. 10 - CAYUCOS WTP · 0 people · 2019 | 9/20 | SYR4 |
| Dichloroacetic Acid | 16.6 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 29.67 µg/L — LOPEZ PROJECT · 1,569 people · 2019 | 10/20 | SYR4 |
| Bromoform | 3.815 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 20 µg/L — AFUERA DE CHORRO WATER COMPANY · 85 people · 2019 | 12/20 | SYR4 |
| Trichloroacetic Acid | 19.7 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019 | 8/20 | SYR4 |
| Monochloroacetic Acid | 2.6 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 18.8 µg/L — SLO CSA NO. 10 - CAYUCOS WTP · 0 people · 2019 | 5/20 | SYR4 |
| Chromium | 15.1 µg/L 15% of the EPA limit 100 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019 | 8/20 | SYR4 |
| Dibromoacetic Acid | 4 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 12 µg/L — MONTE SERENO MUTUAL BENEFIT WATER · 65 people · 2019 | 11/20 | SYR4 |
| Lithium | 10 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2024 | 1/20 | UCMR-5 |
| Arsenic | 3.55 µg/L 36% of the EPA limit 10 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 9.045 µg/L — LAUREATE WATER COMPANY · 700 people · 2018 | 11/20 | SYR4 |
| Bromate | 8.4 µg/L 84% of the EPA limit 10 µg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019 | 1/20 | SYR4 |
| Combined Uranium | 7.97224 µg/L 27% of the EPA limit 30 µg/L Highest in the city: SANTA YSABEL RANCH MWC · 344 people · 2014 | 3/20 | SYR4 |
| Tetrachloroethylene | 3.46 µg/L 69% of the EPA limit 5 µg/L Highest in the city: HIGUERA APARTMENTS · 30 people · 2017 | 1/20 | SYR4 |
| Toluene | 2.7 µg/L 0.3% of the EPA limit 1000 µg/L Highest in the city: AVILA VALLEY MUTUAL WATER CO · 75 people · 2018 | 2/20 | SYR4 |
| Monobromoacetic Acid | 2 µg/L No EPA limit set Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2019
Highest in the city: 2.606 µg/L — CALIFORNIA MENS COLONY · 15,000 people · 2019 | 5/20 | SYR4 |
| Cadmium | 2.485 µg/L 50% of the EPA limit 5 µg/L Highest in the city: LAS VENTANAS RANCH · 108 people · 2017 | 1/20 | SYR4 |
| 1,1-Dichloroethylene | 1.2 µg/L 17% of the EPA limit 7 µg/L Highest in the city: HIGUERA APARTMENTS · 30 people · 2017 | 1/20 | SYR4 |
| Gross Beta Particle Activity | 1 pCi/L No EPA limit set Highest in the city: NACIMIENTO WATER PROJECT · 0 people · 2019 | 1/20 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: SAN LUIS OBISPO WATER DEPARTMENT · 47,788 people · 2025
Highest in the city: 0.0110 mg/L — HIGUERA APARTMENTS · 30 people · 2021 | 18/20 | 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 San Luis Obispo
Frequently asked questions about San Luis Obispo tap water
Is San Luis Obispo tap water safe to drink?
EPA testing detected 30 contaminants in the water serving San Luis Obispo. 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 San Luis Obispo?
20 public water suppliers report drinking-water monitoring for San Luis Obispo, California to the EPA. Each is listed above with its population served.
What contaminants are in San Luis Obispo's water?
The contaminants EPA monitoring detected in San Luis Obispo include Nitrate-Nitrite, Nitrate, Fluoride, Barium, Copper. 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.