What was found in ZIP 91731
The level at this ZIP's main supplier, the highest level anywhere in it, the EPA limit for each, and where the figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate-Nitrite | 235060 µg/L 2351% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 3/4 | SYR4 |
| Nitrate | 11752 µg/L 118% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 4/4 | SYR4 |
| Fluoride | 697 µg/L 17% of the EPA limit 4000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 990 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Copper | 326.2 µg/L 25% of the EPA limit 1300 µg/L Highest in the ZIP: EL MONTE-CITY, WATER DEPT. · 22,968 people · 2019 | 2/4 | SYR4 |
| Barium | 207 µg/L 10% of the EPA limit 2000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 2/4 | SYR4 |
| Tetrachloroethylene | 110 µg/L 2200% of the EPA limit, at the 95th percentile of samples — 5 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 4/4 | SYR4 |
| Lithium | 91.9 µg/L No EPA limit set Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2025 | 1/4 | UCMR-5 |
| Trichloroethylene | 61 µg/L 1220% of the EPA limit, at the 95th percentile of samples — 5 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 4/4 | SYR4 |
| TTHM | 10 µg/L 13% of the EPA limit 80 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 24.6 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Total Haloacetic Acids (HAA5) | 1.91 µg/L 3.2% of the EPA limit 60 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 20 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Chromium | 18.4 µg/L 18% of the EPA limit 100 µg/L Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| Combined Uranium | 13.7378 µg/L 46% of the EPA limit 30 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 14.2444 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Chloroform | 1.8 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 12.88 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Bromodichloromethane | 2.4 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 12.645 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| 1,1-Dichloroethylene | 12 µg/L 171% of the EPA limit, at the 95th percentile of samples — 7 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 2/4 | SYR4 |
| Dibromochloromethane | 4.43 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 11.46 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Dichloroacetic Acid | 9.95 µg/L No EPA limit set Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| Trichloroacetic Acid | 9.855 µg/L No EPA limit set Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| Carbon Tetrachloride | 7.83 µg/L 157% of the EPA limit, at the 95th percentile of samples — 5 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 3/4 | SYR4 |
| Gross Beta Particle Activity | 5.645 pCi/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2018 | 1/4 | SYR4 |
| trans-1,2-Dichloroethylene | 5.325 µg/L 5.3% of the EPA limit 100 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| Selenium | 5 µg/L 10% of the EPA limit 50 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| Bromoform | 4.6 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 4.89 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Dibromoacetic Acid | 1.91 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 4.41 µg/L — CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 4/4 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 4.4 µg/L 73% of the EPA limit 6 µg/L Highest in the ZIP: EL MONTE-CITY, WATER DEPT. · 22,968 people · 2019 | 1/4 | SYR4 |
| cis-1,2-Dichloroethylene | 3.8 µg/L 5.4% of the EPA limit 70 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 3/4 | SYR4 |
| 1,1,2-Trichloroethane | 3.775 µg/L 76% of the EPA limit 5 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| Dichloromethane | 3.32 µg/L 66% of the EPA limit 5 µg/L Highest in the ZIP: GSWC-SOUTH ARCADIA · 27,072 people · 2019 | 1/4 | SYR4 |
| Arsenic | 3.005 µg/L 30% of the EPA limit 10 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 2/4 | SYR4 |
| Monochloroacetic Acid | 3 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 3/4 | SYR4 |
| 1,2-Dichloropropane | 2.77 µg/L 55% of the EPA limit 5 µg/L Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| 1,2-Dichloroethane | 2.3 µg/L 46% of the EPA limit 5 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| Mercury | 2.01 µg/L 100% of the EPA limit, at the 95th percentile of samples — 2 µg/L Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| Nitrite | 0.4700 µg/L 0% of the EPA limit 1000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019
Highest in the ZIP: 1.491 µg/L — EL MONTE-CITY, WATER DEPT. · 22,968 people · 2019 | 2/4 | SYR4 |
| Lead | 1 µg/L 6.7% of the EPA limit 15 µg/L Highest in the ZIP: CAL/AM WATER COMPANY - SAN MARINO · 47,995 people · 2019 | 1/4 | SYR4 |
| Pentachlorophenol | 0.8470 µg/L 85% of the EPA limit 1 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| Toluene | 0.5200 µg/L 0.1% of the EPA limit 1000 µg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2019 | 1/4 | SYR4 |
| PFOS | 0.0220 µg/L No EPA limit set Highest in the ZIP: GSWC-SOUTH ARCADIA · 27,072 people · 2024 | 2/4 | UCMR-5 |
| Pfba | 0.0100 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2025 | 2/4 | UCMR-5 |
| PFHXS | 0.0070 µg/L No EPA limit set Highest in the ZIP: GSWC-SOUTH ARCADIA · 27,072 people · 2024 | 2/4 | UCMR-5 |
| Pfpea | 0.0056 µg/L No EPA limit set Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2025 | 1/4 | UCMR-5 |
| PFOA | 0.0055 µg/L No EPA limit set Highest in the ZIP: GSWC-SOUTH ARCADIA · 27,072 people · 2024 | 1/4 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: SAN GABRIEL VALLEY WATER CO.-EL MONTE · 248,000 people · 2023 | 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.
Water suppliers serving ZIP 91731
| Supplier | State | Population served |
|---|---|---|
| SAN GABRIEL VALLEY WATER CO.-EL MONTE | CA | 248,000 |
| CAL/AM WATER COMPANY - SAN MARINO | CA | 47,995 |
| GSWC-SOUTH ARCADIA | CA | 27,072 |
| EL MONTE-CITY, WATER DEPT. | CA | 22,968 |
Frequently asked questions about ZIP 91731 tap water
Is the tap water in ZIP 91731 safe to drink?
EPA testing detected 43 contaminants across the water suppliers serving ZIP 91731. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and your utility's annual Consumer Confidence Report for the official status.
Which water suppliers serve ZIP 91731?
4 public water suppliers report EPA drinking-water monitoring for ZIP 91731. Each is listed above with its population served.
What contaminants are in ZIP 91731's water?
EPA monitoring detected Nitrate-Nitrite, Nitrate, Fluoride, Copper, Barium, and others across this ZIP's suppliers. The full list with levels and sources is above.