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San Joaquin County, California — public water systems

At a glance

302 active public water systems are filed under San Joaquin County, California in EPA's SDWIS records, together reporting 776,334 people served. The largest is City of Stockton, which reports serving 191,302 people. 94 are community water systems serving people where they live; the other 208 are non-community systems, such as schools, workplaces, campgrounds and gas stations with their own supply.

Dataset updated . Source: EPA SDWIS/ECHO, refreshed quarterly.

Active systems

302

Population served

776.3K

Community systems

94

Groundwater share

94.7%

How does San Joaquin County compare with other California counties?

San Joaquin County has the 6th-most active public water systems among the 201 counties listed for active California systems in EPA records; among the 72 with 3 or more systems, the median has 73. Its systems report 776,334 people served in total, the 14th-largest county figure in the state and 1.8% of the statewide total. The average system here reports serving 2,571 people, about half of the California average of 5,706. Population figures are what each system reports; people served by more than one system, such as a wholesaler and the town that buys from it, are counted by each.

Where does San Joaquin County's drinking water come from?

By primary water source, San Joaquin County's active systems draw on groundwater (283, 94%), purchased surface water (10, 3.3%), surface water (6, 2%) and purchased groundwater (3, 1%). Overall, 95% rely mainly on groundwater (including purchased groundwater) and 5.3% on surface water, compared with 85% and 15% across California. Groundwater means the system draws its water from wells or springs fed by underground aquifers. The county's largest system, City of Stockton, draws primarily on surface water.

What kinds of water systems operate in San Joaquin County?

San Joaquin County's active systems break down as 94 community systems (31%), 95 non-transient non-community systems (31%) and 113 transient non-community systems (37%). 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. A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. A transient non-community water system serves places where people do not stay long, such as gas stations and campgrounds, and regularly serves at least 25 people a day for at least 60 days a year. EPA lists their owner types as private (75%), local government (23%), federal government (1.3%) and state government (1.3%).

The 50 largest water systems in San Joaquin County

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Active public water systems in San Joaquin County, California
#Water systemCountyPopulation servedTypeSource
1City of StocktonSan Joaquin191,302CommunitySurface water
2California Water Service - StocktonSan Joaquin176,266CommunityPurchased surface water
3Tracy, City ofSan Joaquin96,609CommunitySurface water
4Manteca, City ofSan Joaquin84,928CommunityPurchased surface water
5Lodi, City ofSan Joaquin68,272CommunitySurface water
6City of LathropSan Joaquin35,080CommunityPurchased surface water
7City of Mountain HouseSan Joaquin24,948CommunitySurface water
8Ripon, City ofSan Joaquin15,741CommunityGroundwater
9Escalon, City ofSan Joaquin7,429CommunityGroundwater
10San Joaquin County - Lincoln VillageSan Joaquin5,841CommunityPurchased surface water
11Cdcr California Health Care FacilitySan Joaquin5,551CommunityPurchased surface water
12San Joaquin County-Mokelumne AcresSan Joaquin3,802CommunityGroundwater
13Lockeford Community Serv. Dist.San Joaquin3,572CommunityGroundwater
14Jimmys One StopSan Joaquin2,505Transient non-communityGroundwater
15San Joaquin County - Colonial HeightsSan Joaquin1,841CommunityPurchased surface water
16Linden County Water DistrictSan Joaquin1,784CommunityGroundwater
17Little Potato Slough MutualSan Joaquin1,510CommunitySurface water
18Oakwood Lake Water District-SubdivisionSan Joaquin1,479CommunityGroundwater
19Defense Distrib. Depot - Tracy SiteSan Joaquin1,200Non-transient non-communityGroundwater
20StarbucksSan Joaquin1,200Transient non-communityGroundwater
21Fairoaks Pws #44San Joaquin1,172CommunityGroundwater
22Family Market Water SystemSan Joaquin1,105Transient non-communityGroundwater
23San Joaquin County-Raymus VillageSan Joaquin1,086CommunityGroundwater
24Sjc Micke Grove ParkSan Joaquin1,025Non-transient non-communityGroundwater
25Escalon Golf Course WsSan Joaquin1,010Transient non-communityGroundwater
26Horizon Christian FellowshipSan Joaquin1,000Transient non-communityGroundwater
27Jahant Food N Fuel StopSan Joaquin1,000Transient non-communityGroundwater
28King Island Resort PwsSan Joaquin1,000Transient non-communityGroundwater
29Smk ChevronSan Joaquin1,000Transient non-communityGroundwater
30San Joaquin County - ThorntonSan Joaquin964CommunityGroundwater
31St Marys High SchoolSan Joaquin950Non-transient non-communityGroundwater
32San Joaquin County - Wilkinson ManorSan Joaquin851CommunityGroundwater
33Navarra Water SystemSan Joaquin730Transient non-communityGroundwater
34Stockton Verde Mobile Home ParkSan Joaquin711CommunityGroundwater
35Lodi Usd-Davis SchoolSan Joaquin630Non-transient non-communityGroundwater
36San Joaquin River Club Inc.San Joaquin600CommunityGroundwater
37Musd-New Haven SchoolSan Joaquin600Non-transient non-communityGroundwater
38Rodeway InnSan Joaquin600Transient non-communityGroundwater
39Central Valley Baptist Church WsSan Joaquin556Non-transient non-communityGroundwater
40Harney Lane Migrant Center WsSan Joaquin500Non-transient non-communityGroundwater
41Defense Distrib. Depot, Sharpe SiteSan Joaquin500Non-transient non-communityGroundwater
42Jefferson Esd-Jefferson SchoolSan Joaquin483Non-transient non-communityGroundwater
43Ripon Usd-Colony Oak SchoolSan Joaquin465Non-transient non-communityGroundwater
44Sutter Home Winery Inc..San Joaquin463Non-transient non-communityGroundwater
45Delicato VineyardsSan Joaquin430Non-transient non-communityGroundwater
46Morada Estates N Pws #46San Joaquin426CommunityGroundwater
47Lodi Usd-Houston SchoolSan Joaquin405Non-transient non-communityGroundwater
48WienerschnitzelSan Joaquin400Transient non-communityGroundwater
49Oak View Union Elementary SchSan Joaquin350Non-transient non-communityGroundwater
50Musco Family Olive CoSan Joaquin348Non-transient non-communityGroundwater

All other water systems in San Joaquin County (252)

The remaining active systems filed under San Joaquin County, largest first, with the population each reports serving.

San Joaquin County water systems: frequently asked questions

How many public water systems are in San Joaquin County, California?

EPA's SDWIS records file 302 active public water systems under San Joaquin County, California: 94 community systems (31%), 95 non-transient non-community systems (31%) and 113 transient non-community systems (37%).

Who supplies drinking water in San Joaquin County, CA?

The largest community water systems filed under San Joaquin County are City of Stockton (191,302 people served), California Water Service - Stockton (176,266 people served) and City of Tracy (96,609 people served). Which system serves a particular address depends on its service area, which EPA's SDWIS records do not include; a water bill or the local utility can confirm it.

Does San Joaquin County's drinking water come from groundwater or surface water?

Of the 302 active public water systems in San Joaquin County, 95% draw mainly on groundwater and 5.3% on surface water, counting purchased supplies. The largest system, City of Stockton, uses surface water.

Where can I find a water quality report for San Joaquin County?

Each community water system must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1, covering the previous calendar year. 94 community systems are filed under San Joaquin County, so the report to look for is the one from the system that supplies your address.

How can I check violations for a water system in San Joaquin County?

Open the system's profile from the list on this page. Each profile shows the most recent Safe Drinking Water Act violations in EPA's records, with plain-English labels and whether each one is resolved. For current compliance status, EPA ECHO is the primary source.

More California water systems

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, “Public water systems in San Joaquin County, California”, https://aquacensus.com/water-systems/california/san-joaquin (data as of October 1, 2026).