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Tap water quality report

La Mesa, CA

EPA monitoring detected 22 contaminants across the 2 water suppliers serving La Mesa. 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.

2
water suppliers
278,068
people served
22
contaminants found
California rankings Lead in California PFAS in California

What was found in La Mesa'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
Nitrate-Nitrite
483000 µg/L 4830%
of the EPA limit, at the 95th percentile of samples — 10000 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Nitrate
499.58 µg/L 5%
of the EPA limit 10000 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
Highest in the city: 1400 µg/L — TWIN LAKES RESORT · 400 people · 2019
2/2 SYR4
Fluoride
790 µg/L 20%
of the EPA limit 4000 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
2/2 SYR4
Barium
120 µg/L 6%
of the EPA limit 2000 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
TTHM
48 µg/L 60%
of the EPA limit 80 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Combined Uranium
10.4196 µg/L 35%
of the EPA limit 30 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2018
Highest in the city: 34.7617 µg/L — TWIN LAKES RESORT · 400 people · 2018
2/2 SYR4
Lithium
26 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2024
1/2 UCMR-5
Dibromochloromethane
19.95 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Bromodichloromethane
14 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Total Haloacetic Acids (HAA5)
14 µg/L 23%
of the EPA limit 60 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Arsenic
3.125 µg/L 31%
of the EPA limit 10 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
Highest in the city: 12 µg/L — TWIN LAKES RESORT · 400 people · 2019
2/2 SYR4
Bromoform
12 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Chloroform
11 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Bromate
8.87 µg/L 89%
of the EPA limit 10 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Dichloroacetic Acid
7.4 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Selenium
7.2 µg/L 14%
of the EPA limit 50 µg/L
Highest in the city: TWIN LAKES RESORT · 400 people · 2019
1/2 SYR4
Dibromoacetic Acid
3.9 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Trichloroacetic Acid
3.7 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Mercury
1.885 µg/L 94%
of the EPA limit 2 µg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Monobromoacetic Acid
1.48 µg/L
No EPA limit set
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2019
1/2 SYR4
Nitrite
0.1600 µg/L 0%
of the EPA limit 1000 µg/L
Highest in the city: TWIN LAKES RESORT · 400 people · 2018
1/2 SYR4
Lead
0.0 mg/L 0%
of the EPA limit 0.0150 mg/L
Main supplier: HELIX WATER DISTRICT · 277,668 people · 2024
2/2 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 La Mesa

SupplierPopulation served
HELIX WATER DISTRICT 277,668
TWIN LAKES RESORT 400

Frequently asked questions about La Mesa tap water

Is La Mesa tap water safe to drink?

EPA testing detected 22 contaminants in the water serving La Mesa. 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 La Mesa?

2 public water suppliers report drinking-water monitoring for La Mesa, California to the EPA. Each is listed above with its population served.

What contaminants are in La Mesa's water?

The contaminants EPA monitoring detected in La Mesa include Nitrate-Nitrite, Nitrate, Fluoride, Barium, TTHM. 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.