Is San Jose, MP Tap Water Safe? Quality & Contaminants

What was found in San Jose'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	4400 µg/L 44% of the EPA limit 10000 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019	2/4	SYR4
Fluoride	110 µg/L 2.8% of the EPA limit 4000 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019 Highest in the city: 259.5 µg/L — Modern Stationary · 60 people · 2018	2/4	SYR4
Selenium	29.1 µg/L 58% of the EPA limit 50 µg/L Highest in the city: Modern Stationary · 60 people · 2018	1/4	SYR4
TTHM	13.6 µg/L 17% of the EPA limit 80 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019 Highest in the city: 14.69 µg/L — Modern Stationary · 60 people · 2018	3/4	SYR4
Combined Uranium	6.407 µg/L 21% of the EPA limit 30 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019	2/4	SYR4
Barium	3.085 µg/L 0.2% of the EPA limit 2000 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019 Highest in the city: 4.625 µg/L — Modern Stationary · 60 people · 2018	2/4	SYR4
Gross Alpha, Excl. Radon And U	4.235 pCi/L 28% of the EPA limit 15 pCi/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019	2/4	SYR4
Total Haloacetic Acids (HAA5)	3.3 µg/L 5.5% of the EPA limit 60 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019 Highest in the city: 3.575 µg/L — Modern Stationary · 60 people · 2018	2/4	SYR4
Chromium	1.6 µg/L 1.6% of the EPA limit 100 µg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019	2/4	SYR4
Combined Radium (-226 And -228)	1.515 pCi/L 30% of the EPA limit 5 pCi/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2019	2/4	SYR4
Picloram	0.1400 µg/L 0% of the EPA limit 500 µg/L Highest in the city: Modern Stationary · 60 people · 2018	1/4	SYR4
Lead	0.0015 mg/L 10% of the EPA limit 0.0150 mg/L Main supplier: Commonwealth Utilities Corp (Tinian) · 3,005 people · 2025 Highest in the city: 0.0057 mg/L — San Jose Mart Water · 130 people · 2025	4/4	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 San Jose

Supplier	Population served
Commonwealth Utilities Corp (Tinian)	3,005
Tinian Ice And Water	300
San Jose Mart Water	130
Modern Stationary	60

Frequently asked questions about San Jose tap water

Is San Jose tap water safe to drink?

EPA testing detected 12 contaminants in the water serving San Jose. 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 Jose?

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

What contaminants are in San Jose's water?

The contaminants EPA monitoring detected in San Jose include Nitrate, Fluoride, Selenium, TTHM, Combined Uranium. 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.