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Tap water quality report

Cupertino, CA

EPA monitoring detected 5 contaminants across the 1 water supplier serving Cupertino. 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
16,336
people served
5
contaminants found
California rankings Lead in California PFAS in California

What was found in Cupertino'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
4520 µg/L 45%
of the EPA limit 10000 µg/L
Main supplier: CITY OF CUPERTINO · 16,336 people · 2019
1/1 SYR4
Nitrate-Nitrite
4455 µg/L 45%
of the EPA limit 10000 µg/L
Main supplier: CITY OF CUPERTINO · 16,336 people · 2019
1/1 SYR4
Fluoride
202.5 µg/L 5.1%
of the EPA limit 4000 µg/L
Main supplier: CITY OF CUPERTINO · 16,336 people · 2019
1/1 SYR4
Barium
120 µg/L 6%
of the EPA limit 2000 µg/L
Main supplier: CITY OF CUPERTINO · 16,336 people · 2019
1/1 SYR4
Lead
0.0 mg/L 0%
of the EPA limit 0.0150 mg/L
Main supplier: CITY OF CUPERTINO · 16,336 people · 2022
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 Cupertino

SupplierPopulation served
CITY OF CUPERTINO 16,336

Frequently asked questions about Cupertino tap water

Is Cupertino tap water safe to drink?

EPA testing detected 5 contaminants in the water serving Cupertino. 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 Cupertino?

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

What contaminants are in Cupertino's water?

The contaminants EPA monitoring detected in Cupertino include Nitrate, Nitrate-Nitrite, Fluoride, Barium, Lead. 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.