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California Water Service - San Carlos

EPA monitoring tested this supplier for 43 contaminants and detected 12. A detection doesn't automatically mean the water is unsafe — the level and EPA source for each is below.

43
contaminants tested
12
detected
35,344
people served
8
health-based violations
California rankingsLead in CaliforniaPFAS in California
Water source
SWP
Ownership
Private
Counties served
San Mateo

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

8
health-based violations
8
violations on file
0
still open
ViolationTypeStatusPeriod
TT Health-based Resolved 2015-03-01 → 2015-03-31
TT Health-based Resolved 2015-03-01 → 2015-03-31
MCL Health-based Resolved 1996-06-01 → 1996-06-30
MCL Health-based Resolved 1996-06-01 → 1996-06-30
MCL Health-based Resolved 1995-12-01 → 1995-12-31
MCL Health-based Resolved 1995-12-01 → 1995-12-31
TT Health-based Resolved 1993-06-01 → 1993-06-30
TT Health-based Resolved 1993-06-01 → 1993-06-30

Other contaminants detected

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.
ContaminantLevel vs EPA limitDetection rateSourcePeriod
Dichloroacetic Acid
39 µg/L
No EPA limit set
 130/130 SYR4 2012–2019
Total Haloacetic Acids (HAA5)
69 µg/L 115%
of the EPA limit, in the worst sample — 60 µg/L
 130/130 SYR4 2012–2019
Trichloroacetic Acid
28 µg/L
No EPA limit set
 130/130 SYR4 2012–2019
Chloroform
62 µg/L
No EPA limit set
 128/128 SYR4 2012–2019
TTHM
70.1 µg/L 88%
of the EPA limit 80 µg/L
 128/128 SYR4 2012–2019
Bromodichloromethane
10.51 µg/L
No EPA limit set
 120/128 SYR4 2012–2019
Lead
0.0058 mg/L 39%
of the EPA limit 0.0150 mg/L
 42/42 LCR 2024
Dibromochloromethane
2.62 µg/L
No EPA limit set
 24/128 SYR4 2012–2019
Monochloroacetic Acid
30 µg/L
No EPA limit set
 18/130 SYR4 2012–2019
Bromoform
1.37 µg/L
No EPA limit set
 2/128 SYR4 2012–2019
Dibromoacetic Acid
1 µg/L
No EPA limit set
 1/130 SYR4 2012–2019
Monobromoacetic Acid
1.1 µg/L
No EPA limit set
 1/130 SYR4 2012–2019
31 contaminants tested, none detected
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Utility contact

Contact
JAMES, SOPHIE
Phone
408-367-8593
Email
sjames@calwater.com

Frequently asked questions about California Water Service - San Carlos

Is California Water Service - San Carlos tap water safe to drink?

EPA monitoring detected 12 contaminants in California Water Service - San Carlos's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in California Water Service - San Carlos's water?

EPA monitoring detected Dichloroacetic Acid, Total Haloacetic Acids (HAA5), Trichloroacetic Acid, Chloroform, TTHM, and others. The full list with the level and data source for each is above.

How many people does California Water Service - San Carlos serve?

California Water Service - San Carlos reports serving 35,344 people in California, per its EPA record.

Has California Water Service - San Carlos had any water quality violations?

The EPA has 8 violations on file for California Water Service - San Carlos, of which 8 are health-based (a contaminant limit or required treatment was breached) and 0 remain open. The rest are monitoring or reporting failures.

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.