What was found in Riverside'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 | 359550 µg/L 3596% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2018 | 1/6 | SYR4 |
| Nitrate | 10170 µg/L 102% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 19210 µg/L — WESTERN MWD (ARLINGTON) · 0 people · 2019 | 4/6 | SYR4 |
| Fluoride | 750 µg/L 19% of the EPA limit 4000 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 975 µg/L — HARMONY HAVEN · 54 people · 2018 | 4/6 | SYR4 |
| Copper | 135.75 µg/L 10% of the EPA limit 1300 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 700 µg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2019 | 3/6 | SYR4 |
| Barium | 65 µg/L 3.3% of the EPA limit 2000 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 295 µg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2018 | 4/6 | SYR4 |
| Combined Uranium | 41.72 µg/L 139% of the EPA limit, at the 95th percentile of samples — 30 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 3/6 | SYR4 |
| Lithium | 9.1 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2023
Highest in the city: 37 µg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2025 | 3/6 | UCMR-5 |
| Monochloroacetic Acid | 32.7 µg/L No EPA limit set Highest in the city: WESTERN MWD · 86,062 people · 2019 | 4/6 | SYR4 |
| TTHM | 5.6 µg/L 7% of the EPA limit 80 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 30.05 µg/L — WESTERN MWD · 86,062 people · 2019 | 5/6 | SYR4 |
| Total Haloacetic Acids (HAA5) | 25.2 µg/L 42% of the EPA limit 60 µg/L Highest in the city: WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2019 | 4/6 | SYR4 |
| Arsenic | 8 µg/L 80% of the EPA limit 10 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 18.95 µg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2019 | 4/6 | SYR4 |
| Chloroform | 9.732 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 13 µg/L — WESTERN MWD · 86,062 people · 2019 | 5/6 | SYR4 |
| Gross Beta Particle Activity | 13 pCi/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Bromoform | 2.9 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 12 µg/L — WESTERN MWD · 86,062 people · 2019 | 5/6 | SYR4 |
| Dibromochloromethane | 2.9 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 11 µg/L — WESTERN MWD · 86,062 people · 2019 | 5/6 | SYR4 |
| Trichloroethylene | 11 µg/L 220% of the EPA limit, at the 95th percentile of samples — 5 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Chromium | 10.55 µg/L 11% of the EPA limit 100 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 3/6 | SYR4 |
| Bromodichloromethane | 1.97 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 9.28 µg/L — WESTERN MWD (ID A - RAINBOW) · 192 people · 2019 | 5/6 | SYR4 |
| Lead | 8.355 µg/L 56% of the EPA limit 15 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Selenium | 6.6 µg/L 13% of the EPA limit 50 µg/L Highest in the city: WESTERN MWD (ARLINGTON) · 0 people · 2019 | 2/6 | SYR4 |
| Dichloroacetic Acid | 6.225 µg/L No EPA limit set Highest in the city: WESTERN MWD (ID A - RAINBOW) · 192 people · 2019 | 4/6 | SYR4 |
| Picloram | 4.95 µg/L 1% of the EPA limit 500 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Dibromoacetic Acid | 1.7 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019
Highest in the city: 4.9 µg/L — WESTERN MWD · 86,062 people · 2019 | 5/6 | SYR4 |
| Trichloroacetic Acid | 4.02 µg/L No EPA limit set Highest in the city: WESTERN MWD (ID A - RAINBOW) · 192 people · 2019 | 3/6 | SYR4 |
| Combined Radium (-226 And -228) | 4.005 pCi/L 80% of the EPA limit 5 pCi/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Monobromoacetic Acid | 3.195 µg/L No EPA limit set Highest in the city: WESTERN MWD · 86,062 people · 2019 | 4/6 | SYR4 |
| 1,1-Dichloroethylene | 2.3 µg/L 33% of the EPA limit 7 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Dichloromethane | 1.905 µg/L 38% of the EPA limit 5 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 1/6 | SYR4 |
| Tetrachloroethylene | 1.0915 µg/L 22% of the EPA limit 5 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 2/6 | SYR4 |
| 1,2-DIBROMO-3-CHLOROPROPANE | 0.2900 µg/L 145% of the EPA limit, at the 95th percentile of samples — 0.2000 µg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2019 | 2/6 | SYR4 |
| Pfpea | 0.0067 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2023 | 2/6 | UCMR-5 |
| PFOS | 0.0040 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2023
Highest in the city: 0.0057 µg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2025 | 2/6 | UCMR-5 |
| PFOA | 0.0055 µg/L No EPA limit set Highest in the city: WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2025 | 1/6 | UCMR-5 |
| Pfhxa | 0.0041 µg/L No EPA limit set Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2023 | 1/6 | UCMR-5 |
| PFHXS | 0.0041 µg/L No EPA limit set Highest in the city: WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2025 | 2/6 | UCMR-5 |
| PFBS | 0.0030 µg/L No EPA limit set Highest in the city: WESTERN MWD · 86,062 people · 2023 | 1/6 | UCMR-5 |
| Lead | 0.0010 mg/L 6.7% of the EPA limit 0.0150 mg/L Main supplier: RIVERSIDE, CITY OF · 298,398 people · 2025
Highest in the city: 0.0015 mg/L — WESTERN MWD - MURRIETA DIVISION · 17,453 people · 2025 | 5/6 | 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 Riverside
| Supplier | Population served |
|---|---|
| RIVERSIDE, CITY OF | 298,398 |
| WESTERN MWD | 86,062 |
| WESTERN MWD - MURRIETA DIVISION | 17,453 |
| WESTERN MWD (ID A - RAINBOW) | 192 |
| HARMONY HAVEN | 54 |
| WESTERN MWD (ARLINGTON) | 0 |
Frequently asked questions about Riverside tap water
Is Riverside tap water safe to drink?
EPA testing detected 37 contaminants in the water serving Riverside. 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 Riverside?
6 public water suppliers report drinking-water monitoring for Riverside, California to the EPA. Each is listed above with its population served.
What contaminants are in Riverside's water?
The contaminants EPA monitoring detected in Riverside include Nitrate-Nitrite, Nitrate, Fluoride, Copper, 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.