What was found in ZIP 91791
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 | 5650 µg/L 56% of the EPA limit 10000 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 12000 µg/L — AZUSA LIGHT AND WATER · 110,044 people · 2019 | 3/4 | SYR4 |
| Nitrate-Nitrite | 5540 µg/L 55% of the EPA limit 10000 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 10780 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2019 | 2/4 | SYR4 |
| Fluoride | 470 µg/L 12% of the EPA limit 4000 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 477.5 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2019 | 3/4 | SYR4 |
| Barium | 150 µg/L 7.5% of the EPA limit 2000 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 222 µg/L — AZUSA LIGHT AND WATER · 110,044 people · 2019 | 3/4 | SYR4 |
| TTHM | 50.75 µg/L 63% of the EPA limit 80 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 81.35 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Lithium | 54 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2025 | 3/4 | UCMR-5 |
| Chloroform | 20.45 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 42 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Total Haloacetic Acids (HAA5) | 18 µg/L 30% of the EPA limit 60 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 35.4 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Dibromochloromethane | 14 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 29.8 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Bromoform | 6.975 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 25 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2019 | 4/4 | SYR4 |
| Combined Uranium | 2.21265 µg/L 7.4% of the EPA limit 30 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2016
Highest in the ZIP: 23.84 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2019 | 3/4 | SYR4 |
| Dichloroacetic Acid | 11 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 23 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 22 µg/L 367% of the EPA limit, at the 95th percentile of samples — 6 µg/L Highest in the ZIP: VALENCIA HEIGHTS WATER CO. · 7,775 people · 2018 | 2/4 | SYR4 |
| Bromodichloromethane | 16 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 20 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Trichloroacetic Acid | 7.5 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 17.4 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Chromium | 16.7 µg/L 17% of the EPA limit 100 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| Arsenic | 2.49 µg/L 25% of the EPA limit 10 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 16 µg/L — AZUSA LIGHT AND WATER · 110,044 people · 2019 | 2/4 | SYR4 |
| Dibromoacetic Acid | 4.6 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019
Highest in the ZIP: 10.2 µg/L — COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 4/4 | SYR4 |
| Trichloroethylene | 7.7 µg/L 154% of the EPA limit, at the 95th percentile of samples — 5 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| Monobromoacetic Acid | 6.7 µg/L No EPA limit set Highest in the ZIP: COVINA-CITY, WATER DEPT. · 33,300 people · 2019 | 2/4 | SYR4 |
| Selenium | 5.2 µg/L 10% of the EPA limit 50 µg/L Highest in the ZIP: VALENCIA HEIGHTS WATER CO. · 7,775 people · 2019 | 1/4 | SYR4 |
| 1,1-Dichloroethylene | 3.7 µg/L 53% of the EPA limit 7 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| Tetrachloroethylene | 1.9 µg/L 38% of the EPA limit 5 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 2/4 | SYR4 |
| Chlorobenzene | 1.329 µg/L 1.3% of the EPA limit 100 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| trans-1,2-Dichloroethylene | 1.3 µg/L 1.3% of the EPA limit 100 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| cis-1,2-Dichloroethylene | 1.2 µg/L 1.7% of the EPA limit 70 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| Carbon Tetrachloride | 0.6590 µg/L 13% of the EPA limit 5 µg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2019 | 1/4 | SYR4 |
| PFOA | 0.0077 µg/L No EPA limit set Highest in the ZIP: AZUSA LIGHT AND WATER · 110,044 people · 2024 | 2/4 | UCMR-5 |
| Pfba | 0.0062 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2025 | 1/4 | UCMR-5 |
| PFOS | 0.0058 µg/L No EPA limit set Highest in the ZIP: AZUSA LIGHT AND WATER · 110,044 people · 2024 | 2/4 | UCMR-5 |
| PFBS | 0.0036 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2025
Highest in the ZIP: 0.0044 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2024 | 2/4 | UCMR-5 |
| Pfhxa | 0.0033 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2025
Highest in the ZIP: 0.0043 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2024 | 3/4 | UCMR-5 |
| Pfpea | 0.0035 µg/L No EPA limit set Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 people · 2025
Highest in the ZIP: 0.0040 µg/L — VALENCIA HEIGHTS WATER CO. · 7,775 people · 2024 | 2/4 | UCMR-5 |
| PFHXS | 0.0036 µg/L No EPA limit set Highest in the ZIP: VALENCIA HEIGHTS WATER CO. · 7,775 people · 2024 | 1/4 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: SUBURBAN WATER SYSTEMS-SAN JOSE · 168,843 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.
Water suppliers serving ZIP 91791
| Supplier | State | Population served |
|---|---|---|
| SUBURBAN WATER SYSTEMS-SAN JOSE | CA | 168,843 |
| AZUSA LIGHT AND WATER | CA | 110,044 |
| COVINA-CITY, WATER DEPT. | CA | 33,300 |
| VALENCIA HEIGHTS WATER CO. | CA | 7,775 |
Frequently asked questions about ZIP 91791 tap water
Is the tap water in ZIP 91791 safe to drink?
EPA testing detected 35 contaminants across the water suppliers serving ZIP 91791. 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 91791?
4 public water suppliers report EPA drinking-water monitoring for ZIP 91791. Each is listed above with its population served.
What contaminants are in ZIP 91791's water?
EPA monitoring detected Nitrate, Nitrate-Nitrite, Fluoride, Barium, TTHM, and others across this ZIP's suppliers. The full list with levels and sources is above.