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California Water Service - San Mateo

Published drinking-water records and contacts for California Water Service - San Mateo. System CA4110008. Review sources and dates; not a real-time water assessment.

System ID
CA4110008
State or territory
CA
Published population served
102348
System type (source code)
CWS

Published records and dates

Missing records here do not mean the provider did not test. Published records are not a real-time assessment of your tap water.

Published testing results

Selected recent records are shown below. Different sampling locations and dates are not interchangeable. These excerpts are not a complete testing history.

“<” means below the stated reporting limit, not zero. A reported measurement alone is not a safety verdict. Read an example

EPA UCMR 5 — most recent imported sample per substance
SubstancePublished resultReporting limitSample dateSampling location
11Cl-PF3OUdS< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
4:2 FTS< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
6:2 FTS< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
8:2 FTS< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
9Cl-PF3ONS< 0.002 µg/L0.002 µg/L2025-02-03SFWD Intertie / 4110008002
ADONA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
HFPO-DA< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
NEtFOSAA< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
NFDHA< 0.02 µg/L0.02 µg/L2025-02-03SFWD Intertie / 4110008002
NMeFOSAA< 0.006 µg/L0.006 µg/L2025-02-03SFWD Intertie / 4110008002
PFBA< 0.005 µg/L0.005 µg/L2025-02-03SFWD Intertie / 4110008002
PFBS< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFDA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFDoA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFEESA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFHpA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFHpS< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFHxA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFHxS< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFMBA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFMPA< 0.004 µg/L0.004 µg/L2025-02-03SFWD Intertie / 4110008002
PFNA< 0.004 µg/L0.004 µg/L2025-02-03SFWD Intertie / 4110008002
PFOA< 0.004 µg/L0.004 µg/L2025-02-03SFWD Intertie / 4110008002
PFOS< 0.004 µg/L0.004 µg/L2025-02-03SFWD Intertie / 4110008002
PFPeA< 0.003 µg/L0.003 µg/L2025-02-03SFWD Intertie / 4110008002
PFPeS< 0.004 µg/L0.004 µg/L2025-02-03SFWD Intertie / 4110008002
PFTA< 0.008 µg/L0.008 µg/L2025-02-03SFWD Intertie / 4110008002
PFTrDA< 0.007 µg/L0.007 µg/L2025-02-03SFWD Intertie / 4110008002
PFUnA< 0.002 µg/L0.002 µg/L2025-02-03SFWD Intertie / 4110008002
lithium< 9 µg/L9 µg/L2025-02-03SFWD Intertie / 4110008002

Download all EPA UCMR 5 records (CSV)

Lead and copper: 90th-percentile summaries

These describe a monitoring period across sampled locations, not the result at your home. How to read the 90th percentile

Eight most recent imported monitoring summaries
SubstancePublished 90th percentileMonitoring periodSource quarter
Lead (PB90) 0.0044 mg/L2023-01-01 – 2025-12-312026Q3
Lead (PB90) 0.0046 mg/L2020-01-01 – 2022-12-312026Q3
Lead (PB90) 0.00594 mg/L2017-01-01 – 2019-12-312026Q3
Lead (PB90) 0 mg/L2016-01-01 – 2018-12-312026Q3
Lead (PB90) 0.0088 mg/L2013-01-01 – 2015-12-312026Q3
Lead (PB90) 0 mg/L2010-01-01 – 2012-12-312026Q3
Lead (PB90) 0 mg/L2005-01-01 – 2007-12-312026Q3
Lead (PB90) 0.0038 mg/L2006-01-01 – 2006-12-312026Q3
Twelve most recent imported state laboratory records
SubstancePublished resultSample dateLocation / source
BROMODICHLOROMETHANE2.9 UG/L2026-05-06DBPR Sample / California DDW laboratory results
MONOBROMOACETIC ACID< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
CHLOROFORM32 UG/L2026-05-06DBPR Sample / California DDW laboratory results
MONOCHLOROACETIC ACID< 2.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
DIBROMOACETIC ACID< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
MONOCHLOROACETIC ACID2.1 UG/L2026-05-06DBPR Sample / California DDW laboratory results
DIBROMOCHLOROMETHANE< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
MONOBROMOACETIC ACID< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
TTHM45 UG/L2026-05-06DBPR Sample / California DDW laboratory results
DIBROMOCHLOROMETHANE< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results
DICHLOROACETIC ACID31 UG/L2026-05-06DBPR Sample / California DDW laboratory results
MONOBROMOACETIC ACID< 1.000000000 UG/L2026-05-06DBPR Sample / California DDW laboratory results

State sampling points can include untreated water. Publisher qualifiers and units are retained; consult the full source notes before interpreting a record.

Download state records with source notes (CSV)

Published compliance history

0 imported records. Status is as recorded in the source; historical records are not current advisories. Missing records do not establish that no violations occurred.

Source dates and refresh checks

A refresh check is not a sample date. Publication periods, sample dates and checks are shown separately.

Administrative contact (EPA filing)

James, Sophie: 408-367-8593

An administrative filing contact may not be a customer-service line. Confirm current contact details with the provider.

Official state resources · How to read these records