Stanislaus County, California — public water systems
At a glance
191 active public water systems are filed under Stanislaus County, California in EPA's SDWIS records, together reporting 512,656 people served. The largest is City of Modesto, which reports serving 218,771 people. 60 are community water systems serving people where they live; the other 131 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
191
Population served
512.7K
Community systems
60
Groundwater share
92.7%
How does Stanislaus County compare with other California counties?
Stanislaus County has the 12th-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 512,656 people served in total, the 16th-largest county figure in the state and 1.2% of the statewide total. The average system here reports serving 2,684 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 Stanislaus County's drinking water come from?
By primary water source, Stanislaus County's active systems draw on groundwater (174, 91%), purchased surface water (8, 4.2%), surface water (6, 3.1%) and purchased groundwater (2, 1%). Overall, 93% rely mainly on groundwater (including purchased groundwater) and 7.3% 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 Modesto, draws primarily on purchased surface water.
What kinds of water systems operate in Stanislaus County?
Stanislaus County's active systems break down as 60 community systems (31%), 64 non-transient non-community systems (34%) and 67 transient non-community systems (35%). 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 (68%), local government (30%), federal government (1%) and state government (0.5%).
The 50 largest water systems in Stanislaus County
🔒 Create a free account to export CSV| # | Water system | County | Population served | Type | Source |
|---|---|---|---|---|---|
| 1 | Modesto, City of | Stanislaus | 218,771 | Community | Purchased surface water |
| 2 | Turlock, City of | Stanislaus | 72,682 | Community | Purchased surface water |
| 3 | Ceres, City of | Stanislaus | 54,513 | Community | Purchased surface water |
| 4 | Patterson, City of | Stanislaus | 24,977 | Community | Groundwater |
| 5 | Riverbank, City of | Stanislaus | 24,834 | Community | Groundwater |
| 6 | Oakdale, City of | Stanislaus | 23,235 | Community | Groundwater |
| 7 | City of Modesto - Salida | Stanislaus | 14,537 | Community | Purchased surface water |
| 8 | City of Newman-Water Department | Stanislaus | 12,207 | Community | Groundwater |
| 9 | City of Waterford | Stanislaus | 8,788 | Community | Groundwater |
| 10 | Hughson, City of | Stanislaus | 7,481 | Community | Groundwater |
| 11 | Keyes Community Services Dist. | Stanislaus | 5,672 | Community | Groundwater |
| 12 | Denair Community Services District | Stanislaus | 5,090 | Community | Groundwater |
| 13 | Joe'S Travel Plaza (Eh) | Stanislaus | 5,026 | Non-transient non-community | Groundwater |
| 14 | Department of Transportation | Stanislaus | 4,375 | Transient non-community | Groundwater |
| 15 | Western Hills Water District/Diablo Gran | Stanislaus | 2,000 | Community | Surface water |
| 16 | Gregori High School | Stanislaus | 2,000 | Non-transient non-community | Groundwater |
| 17 | Oid-Oakdale Rural Water System #1 | Stanislaus | 1,570 | Community | Groundwater |
| 18 | City of Modesto - Del Rio | Stanislaus | 1,327 | Community | Groundwater |
| 19 | City of Modesto - South Turlock | Stanislaus | 1,099 | Community | Purchased surface water |
| 20 | Waterford-River Pointe | Stanislaus | 1,079 | Community | Groundwater |
| 21 | Our Lady of Assumption Church | Stanislaus | 1,000 | Transient non-community | Groundwater |
| 22 | City of Modesto - Grayson | Stanislaus | 914 | Community | Groundwater |
| 23 | Hillsview Homes | Stanislaus | 887 | Community | Groundwater |
| 24 | Mesa Elementary School | Stanislaus | 860 | Non-transient non-community | Groundwater |
| 25 | Hart- Ransom Union School & District | Stanislaus | 650 | Non-transient non-community | Groundwater |
| 26 | Riverdale Park Tract Csd | Stanislaus | 610 | Community | Groundwater |
| 27 | Waterford - Hickman | Stanislaus | 597 | Community | Groundwater |
| 28 | Riverview Mobile Home Estates | Stanislaus | 540 | Community | Groundwater |
| 29 | Woodward Reservoir Water System | Stanislaus | 537 | Transient non-community | Groundwater |
| 30 | Jehovah'S Witness Sierra Vista Cong | Stanislaus | 500 | Transient non-community | Groundwater |
| 31 | River Oak Grace-Water System | Stanislaus | 500 | Transient non-community | Groundwater |
| 32 | River Oaks/Kingdom Hall | Stanislaus | 500 | Transient non-community | Groundwater |
| 33 | Crows Landing Comm Svc District | Stanislaus | 500 | Community | Groundwater |
| 34 | Ceres Unified/Westport School | Stanislaus | 450 | Non-transient non-community | Groundwater |
| 35 | Bronco Winery | Stanislaus | 400 | Non-transient non-community | Groundwater |
| 36 | Stanislaus Union School Dist | Stanislaus | 390 | Non-transient non-community | Groundwater |
| 37 | Chatom School (Eh) | Stanislaus | 385 | Non-transient non-community | Groundwater |
| 38 | 5033 Pentecost | Stanislaus | 302 | Non-transient non-community | Groundwater |
| 39 | Nmip Fire & Water System, LLC | Stanislaus | 300 | Non-transient non-community | Groundwater |
| 40 | Covenant Grove Church | Stanislaus | 300 | Transient non-community | Groundwater |
| 41 | Oid #51 - Sunset Oaks #10 | Stanislaus | 287 | Community | Groundwater |
| 42 | Oid #46 - Sunset Oaks | Stanislaus | 269 | Community | Groundwater |
| 43 | Park Heights Mutual Water Co | Stanislaus | 250 | Community | Groundwater |
| 44 | Ram Naam Mandali Church of Modesto | Stanislaus | 250 | Transient non-community | Groundwater |
| 45 | North Oaks Mutual Water Co | Stanislaus | 234 | Community | Groundwater |
| 46 | Paradise School | Stanislaus | 218 | Non-transient non-community | Groundwater |
| 47 | Casa De Amigos Manufactured Housing Comm | Stanislaus | 204 | Community | Groundwater |
| 48 | The Morning Star Company | Stanislaus | 200 | Non-transient non-community | Groundwater |
| 49 | Tid/ La Grange Water System | Stanislaus | 195 | Community | Surface water |
| 50 | Monte Vista Farming | Stanislaus | 188 | Non-transient non-community | Groundwater |
All other water systems in Stanislaus County (140)
The remaining active systems filed under Stanislaus County, largest first, with the population each reports serving.
- Monterey Park Tract Csd186
- City of Modesto - Walnut Manor175
- City of Modesto - North Turlock172
- Sconza Candy Company170
- Mountain View Elementary School170
- Knights Ferry Comm. Svc. Dist.168
- Grace Community Christian Church160
- Riverbank Lra156
- Olive Lane Mobilehome Park153
- Buehner Water System150
- Oid #22 - Williams Tract150
- Mulberry MHP148
- Oid #45144
- Greenlaw Modesto Investors LLC142
- Gratton School141
- Stratos Way Water Company, Inc.135
- Grover Landscape Water System125
- Lazy B Mobilehome Park125
- Libitzky125
- Fisherman'S Bend MHP120
- Kiernan Business Center120
- City of Modesto - Central Turlock119
- The Fruit Yard Restaurant118
- Twin Cypress Mobile Home Park112
- Del Rio East Hoa Water System110
- Gurudwara Guru Nanak Sahib109
- Shiloh School District105
- Roberts Ferry School Cafeteria100
- Ratto Bros, Inc.100
- Kingdom Hall Jehovah Witness100
- Sikh Temple Modesto-Ceres97
- Wood Colony Christian School90
- Valley Home School Texas80
- Hughson Nut Company Water System80
- Oasis Investments75
- Duarte Nursery Inc. Water System75
- New Hope Church of the Nazarene70
- Westley Csd70
- Morningside Mobilehome Park67
- 4n Mobilehome Park65
- Liberty Baptist Church65
- Lone Pine MHP64
- Frazier Nut Farms, Inc..64
- Martin'S Mobile Home Court60
- Country Villa Apts60
- Mid Valley Nut Co60
- Tully Mobile Estates56
- Country Western Mhrv55
- Brethren Heritage School, Inc.50
- Cobles Corner50
- Rbvon50
- One Stop Ws50
- Excell Center45
- Rolling Hills Nut Company45
- Darling Ingredients Turlock43
- Chemurgic Agricultural Chemicals, Inc..42
- Foster Farms-Ellenwood Hatchery40
- Storer Transportation40
- Lakewood Memorial Park & Funeral Home40
- Patterson Cemetery District37
- Maze Blvd Mobilehome Park36
- Sterling Industrial35
- Turlock Sportsman'S Club32
- Fink Road Landfill Stanislaus31
- California Nut Company30
- Tds California30
- Rainbow Farms30
- Jennings Wwtp30
- Lander Veterinary Clinic27
- Mchenry Business Park27
- Shively'S Bar & Grill26
- Whiskey River Saloon26
- Golden Arco26
- Taqueria Rancho Alegre26
- Beckley Lyons Water System26
- Frank Raines Park Ohv26
- Fox Grove Fishing Access26
- La Grange Park-Ohv26
- Basso Bridge Fishing/Boating Access26
- Knights Ferry Recreation Area26
- Shiloh-Paradise Baseball for Youth26
- Foster Farms #526
- Smart Stop Food Mart (Eh)26
- River Road Mutual Water Company26
- 4937 Beckwith Water System26
- Joe'S Food Mart Water System26
- Vfw Post 5059 Water System26
- Fresh Point (Piranha Produce)26
- Valley Home School Pioneer26
- Farmers' Den /Market26
- City of Oakdale -Kerr Park26
- Gawfco Enterprises, Inc..26
- Log Cabin26
- 5801 Mchenry Ave26
- Hamlet Motel26
- Eastin26
- Orange Blossom Recreation Area26
- Modesto Christian Center (Watersystem)25
- Oakdale Golf & Country Club (Eh)25
- Bloomingcamp Water System25
- Waterford Sportsmen'S Club25
- Nino'S Place Water System25
- Kiernan/Mchenry Water Company, Inc.25
- J & J Farm Fresh Produce & Bakery25
- Oasis Market25
- Fisher Nut25
- California Transplants LLC25
- Country Store Water System25
- Modesto Reservoir25
- Pioneer Equine Hospital Water System25
- Golden Valley Almonds25
- Mid Valley Ag25
- River Road Plaza25
- Keyes 76 (Water System)25
- Cebro Frozen Foods (Eh)25
- Triangle Truck Stop (Water)25
- Buehner Houses25
- Mountain View Chatom Recreation25
- Full Gospel Assembly25
- South San Joaquin Irrigation District25
- Bel Passi Baseball25
- Avidwater, LLC25
- Village Food Mart Water System25
- Resendiz Fruit Barn25
- Westley Property LLC25
- Roberts Ferry Nut Co, Inc. (Ws)25
- West Coast Sand & Gravel25
- Zansco25
- Elks Lodge 128225
- Growers Direct Nut Company25
- Purina Mills Inc.25
- Salida Hulling Association Water System25
- Fee Water System25
- Los Indios Water System25
- Charity Way Water System25
- Pentecost Properties Water System25
- Oakdale Cheese & Specialties25
- Burchell Nursery, Inc.25
- Rainbow Sports Complex25
- Modesto Irrigation District23
Stanislaus County water systems: frequently asked questions
How many public water systems are in Stanislaus County, California?
EPA's SDWIS records file 191 active public water systems under Stanislaus County, California: 60 community systems (31%), 64 non-transient non-community systems (34%) and 67 transient non-community systems (35%).
Who supplies drinking water in Stanislaus County, CA?
The largest community water systems filed under Stanislaus County are City of Modesto (218,771 people served), City of Turlock (72,682 people served) and City of Ceres (54,513 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 Stanislaus County's drinking water come from groundwater or surface water?
Of the 191 active public water systems in Stanislaus County, 93% draw mainly on groundwater and 7.3% on surface water, counting purchased supplies. The largest system, City of Modesto, uses purchased surface water.
Where can I find a water quality report for Stanislaus 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. 60 community systems are filed under Stanislaus 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 Stanislaus 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
- All California public water systems· 7,479 active
- Tulare County· 274 systems
- Madera County· 202 systems
- Riverside County· 197 systems
- San Diego County· 191 systems
- Napa County· 188 systems
- Shasta County· 174 systems
- How to find out who supplies your drinking water
- How to find and read your annual water quality report
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 Stanislaus County, California”, https://aquacensus.com/water-systems/california/stanislaus (data as of October 1, 2026).