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Tap water quality report

Walnut, CA

EPA monitoring detected 13 contaminants across the 1 water supplier serving Walnut. A detection doesn't automatically mean the water is unsafe — see the level at the main supplier for each below, with its EPA source and period.

1
water supplier
100,941
people served
13
contaminants found
California rankings Lead in California PFAS in California

What was found in Walnut'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.

ContaminantLevel vs EPA limitSuppliersSource
TTHM
63.38 µg/L 79%
of the EPA limit 80 µg/L
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Lithium
50.1 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2024
1/1 UCMR-5
Total Haloacetic Acids (HAA5)
33.34 µg/L 56%
of the EPA limit 60 µg/L
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Monochloroacetic Acid
22.34 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Dibromochloromethane
21.925 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Bromodichloromethane
20.84 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Chloroform
18.585 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Dichloroacetic Acid
13.385 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Bromoform
9.06 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Trichloroacetic Acid
8.942 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Dibromoacetic Acid
8.1395 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Monobromoacetic Acid
2.6945 µg/L
No EPA limit set
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2019
1/1 SYR4
Lead
0.0 mg/L 0%
of the EPA limit 0.0150 mg/L
Main supplier: WALNUT VALLEY WATER DISTRICT · 100,941 people · 2024
1/1 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 Walnut

SupplierPopulation served
WALNUT VALLEY WATER DISTRICT 100,941

Frequently asked questions about Walnut tap water

Is Walnut tap water safe to drink?

EPA testing detected 13 contaminants in the water serving Walnut. 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 Walnut?

1 public water supplier report drinking-water monitoring for Walnut, California to the EPA. Each is listed above with its population served.

What contaminants are in Walnut's water?

The contaminants EPA monitoring detected in Walnut include TTHM, Lithium, Total Haloacetic Acids (HAA5), Monochloroacetic Acid, Dibromochloromethane. 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.