Is San Dimas, CA Tap Water Safe? Quality & Contaminants

What was found in San Dimas's water

The highest level seen across the city's suppliers, the EPA limit for each, and where the figure comes from.

Contaminant	Level vs EPA limit	Suppliers	Source
Nitrate	6328 µg/L 63% of the EPA limit 10000 µg/L	1/4	SYR4
Nitrate-Nitrite	5600 µg/L 56% of the EPA limit 10000 µg/L	1/4	SYR4
Fluoride	910 µg/L 23% of the EPA limit 4000 µg/L	1/4	SYR4
Copper	190 µg/L 15% of the EPA limit 1300 µg/L	1/4	SYR4
TTHM	120 µg/L 150% of the EPA limit, in the worst sample — 80 µg/L	4/4	SYR4
Lithium	57 µg/L No EPA limit set	2/4	UCMR-5
Dibromochloromethane	46 µg/L No EPA limit set	4/4	SYR4
Total Haloacetic Acids (HAA5)	38 µg/L 63% of the EPA limit 60 µg/L	4/4	SYR4
Chloroform	36 µg/L No EPA limit set	4/4	SYR4
Bromodichloromethane	34 µg/L No EPA limit set	4/4	SYR4
Bromoform	34 µg/L No EPA limit set	4/4	SYR4
Dichloroacetic Acid	21 µg/L No EPA limit set	3/4	SYR4
Trichloroethylene	20 µg/L 400% of the EPA limit, in the worst sample — 5 µg/L	1/4	SYR4
Dibromoacetic Acid	17 µg/L No EPA limit set	4/4	SYR4
Lead	17 µg/L 113% of the EPA limit, in the worst sample — 15 µg/L	1/4	SYR4
Trichloroacetic Acid	12 µg/L No EPA limit set	3/4	SYR4
Tetrachloroethylene	7.8 µg/L 156% of the EPA limit, in the worst sample — 5 µg/L	1/4	SYR4
Monobromoacetic Acid	6.2 µg/L No EPA limit set	1/4	SYR4
Monochloroacetic Acid	5.7 µg/L No EPA limit set	3/4	SYR4
Combined Uranium	4.619 µg/L 15% of the EPA limit 30 µg/L	1/4	SYR4
Dichloromethane	3.4 µg/L 68% of the EPA limit 5 µg/L	1/4	SYR4
PFOS	0.0220 µg/L No EPA limit set	3/4	UCMR-5
PFOA	0.0129 µg/L No EPA limit set	2/4	UCMR-5
Pfhxa	0.0084 µg/L No EPA limit set	1/4	UCMR-5
PFHXS	0.0070 µg/L No EPA limit set	2/4	UCMR-5
Pfpea	0.0064 µg/L No EPA limit set	1/4	UCMR-5
Lead	0.0056 mg/L 37% of the EPA limit 0.0150 mg/L	4/4	LCR
Pfba	0.0056 µg/L No EPA limit set	1/4	UCMR-5
PFBS	0.0051 µg/L No EPA limit set	1/4	UCMR-5
Pfhpa	0.0046 µg/L No EPA limit set	1/4	UCMR-5

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 single worst sample on record — 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 San Dimas

Supplier	Population served
GSWC-SAN DIMAS	56,538
GSWC - CLAREMONT	39,730
GSWC-SOUTH ARCADIA	27,072
GSWC-SOUTH SAN GABRIEL	26,240

Frequently asked questions about San Dimas tap water

Is San Dimas tap water safe to drink?

EPA testing detected 30 contaminants in the water serving San Dimas. 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 San Dimas?

4 public water suppliers report drinking-water monitoring for San Dimas, California to the EPA. Each is listed above with its population served.

What contaminants are in San Dimas's water?

The contaminants EPA monitoring detected in San Dimas include Nitrate, Nitrate-Nitrite, Fluoride, Copper, TTHM. The full list, with the highest level found 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.