Public water system · CA3910015

Active

City of Lathrop

At a glance

City of Lathrop (PWSID CA3910015) is an active community water system in San Joaquin County, California. It reports serving 35,080 people through 11,185 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in July 2018.

Dataset updated October 2026 . Source: EPA SDWIS/ECHO public records.

Population served

35,080

Service connections

11,185

Primary source

SWP

Purchased surface water

System type

CWS

Community water system

System record

PWSIDCA3910015

System typeCommunity water system

Activity statusActive

Population served35,080

Service connections11,185

Primary water sourcePurchased surface water

Owner typeLocal government

Primacy agencyCA state drinking water program

City servedLathrop

StateCalifornia

ZIP—

CountySan Joaquin County

How does City of Lathrop compare with other water systems in San Joaquin County?

By EPA's size categories, City of Lathrop is a large system (10,001 to 100,000 people). San Joaquin County has 302 active public water systems, and City of Lathrop is the 6th-largest of them by population served. Its population served is about 14 times the county average of 2,571 people per system, and accounts for 4.5% of the 776,334 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so City of Lathrop is about 5.2 times that figure.

What does “community water system” mean?

A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 506 California systems (6.8%) list purchased surface water as their primary source.

Who owns and regulates City of Lathrop?

EPA lists City of Lathrop as owned by a local government. The CA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 69 of the 302 active systems in San Joaquin County (23%) are also owned by a local government.

Does City of Lathrop have drinking water violations?

Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in July 2018. The violations listed here began between April 2013 and July 2018. By type: 10 contaminant level above the legal limit and 2 monitoring and reporting. The contaminant or rule involved most often is Arsenic (5 of them). EPA lists 12 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.

Began	Violation	Contaminant or rule	Health-based	Status
2018-07-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Total trihalomethanes (TTHM)code 2950	No	Resolved
2018-07-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Haloacetic acids (HAA5)code 2456	No	Resolved
2014-04-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Arseniccode 1005	Yes	Resolved
2014-04-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Combined Uraniumcode 4006	Yes	Resolved
2014-01-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Arseniccode 1005	Yes	Resolved
2014-01-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Combined Uraniumcode 4006	Yes	Resolved
2013-10-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Combined Uraniumcode 4006	Yes	Resolved
2013-10-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Arseniccode 1005	Yes	Resolved
2013-07-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Combined Uraniumcode 4006	Yes	Resolved
2013-07-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Arseniccode 1005	Yes	Resolved
2013-04-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Combined Uraniumcode 4006	Yes	Resolved
2013-04-01	Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02	Arseniccode 1005	Yes	Resolved

The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.

City of Lathrop: frequently asked questions

Who runs City of Lathrop?

City of Lathrop (PWSID CA3910015) is a community water system owned by a local government. It is regulated by the CA state drinking water program.

How many people does City of Lathrop serve?

City of Lathrop reports serving 35,080 people through 11,185 service connections in San Joaquin County, California.

Where does City of Lathrop get its water?

EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.

Does City of Lathrop have any drinking water violations?

Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in July 2018. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.

Is City of Lathrop's water safe to drink?

AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in July 2018. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.

Where can I find City of Lathrop's water quality report?

As a community water system, City of Lathrop must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.

Other water systems in San Joaquin County

Water system	County	Population served	Type	Source
City of Stockton	San Joaquin	191,302	Community	Surface water
California Water Service - Stockton	San Joaquin	176,266	Community	Purchased surface water
Tracy, City of	San Joaquin	96,609	Community	Surface water
Manteca, City of	San Joaquin	84,928	Community	Purchased surface water
Lodi, City of	San Joaquin	68,272	Community	Surface water
City of Mountain House	San Joaquin	24,948	Community	Surface water

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About this data

Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.

Cite as: AquaCensus, “City of Lathrop, PWSID CA3910015, California”, https://aquacensus.com/water-systems/california/city-of-lathrop-ca3910015 (data as of October 1, 2026).