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Santa Clara County, California — public water systems

At a glance

121 active public water systems are filed under Santa Clara County, California in EPA's SDWIS records, together reporting 2,097,447 people served. The largest is San Jose Water, which reports serving 1,039,920 people. 74 are community water systems serving people where they live; the other 47 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

121

Population served

2.1M

Community systems

74

Groundwater share

67.8%

How does Santa Clara County compare with other California counties?

Santa Clara County has the 20th-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 2,097,447 people served in total, the 7th-largest county figure in the state and 4.9% of the statewide total. The average system here reports serving 17,334 people, about 3 times 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 Santa Clara County's drinking water come from?

By primary water source, Santa Clara County's active systems draw on groundwater (80, 66%), purchased surface water (28, 23%), surface water (10, 8.3%) and purchased groundwater (2, 1.7%). Overall, 68% rely mainly on groundwater (including purchased groundwater) and 31% 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, San Jose Water, draws primarily on surface water.

What kinds of water systems operate in Santa Clara County?

Santa Clara County's active systems break down as 74 community systems (61%), 22 non-transient non-community systems (18%) and 25 transient non-community systems (21%). 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 (28%), state government (2.5%) and federal government (0.8%).

The 50 largest water systems in Santa Clara County

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Active public water systems in Santa Clara County, California
#Water systemCountyPopulation servedTypeSource
1San Jose WaterSanta Clara1,039,920CommunitySurface water
2City of SunnyvaleSanta Clara157,566CommunityPurchased surface water
3City of Santa ClaraSanta Clara130,746CommunityPurchased surface water
4Great Oaks Wc Inc.Santa Clara110,088CommunityGroundwater
5City of San Jose - Evg/Edv/CoySanta Clara101,265CommunityPurchased surface water
6City of MilpitasSanta Clara81,773CommunityPurchased surface water
7City of Mountain ViewSanta Clara81,501CommunityPurchased surface water
8Cwsc Los Altos SuburbanSanta Clara69,973CommunityPurchased surface water
9City of Palo AltoSanta Clara67,231CommunityPurchased surface water
10City of GilroySanta Clara59,203CommunityGroundwater
11City of Morgan HillSanta Clara47,374CommunityGroundwater
12City of San Jose - Nsj/AlvisoSanta Clara45,559CommunityPurchased surface water
13Stanford UniversitySanta Clara35,853CommunityPurchased surface water
14City of CupertinoSanta Clara16,336CommunityPurchased surface water
15Nasa Ames Research CenterSanta Clara16,273CommunityPurchased surface water
16Purissima Hills Water DistrictSanta Clara6,245CommunityPurchased surface water
17Santa Clara Valley Medical CenterSanta Clara3,000Non-transient non-communityPurchased surface water
18El Camino HospitalSanta Clara3,000Non-transient non-communityPurchased surface water
19O'Connor HospitalSanta Clara2,500Non-transient non-communityPurchased surface water
20Western Digital Technologies, Inc..Santa Clara2,439Non-transient non-communityGroundwater
21Csp Henry W. Coe State ParkSanta Clara1,205Transient non-communityGroundwater
22Cal Am - West San MartinSanta Clara1,173CommunityGroundwater
23Gavilan Joint Community College DistrictSanta Clara989Non-transient non-communityGroundwater
24Christopher Ranch L.L.C.Santa Clara735Non-transient non-communityGroundwater
25San Martin County Water DistrictSanta Clara627CommunityGroundwater
26Mt. Madonna County ParkSanta Clara621Transient non-communityGroundwater
27Loma Prieta Jusd-Loma Prieta SchoolSanta Clara542Non-transient non-communityGroundwater
28Gilroy Usd-Rucker SchoolSanta Clara536Non-transient non-communityGroundwater
29Uvas Canyon County ParkSanta Clara509Transient non-communityGroundwater
30Coyote Valley Rv ResortSanta Clara500CommunityGroundwater
31Cinnabar Hills Golf ClubSanta Clara450Non-transient non-communityPurchased surface water
32Camp SaratogaSanta Clara450CommunitySurface water
33Sanborn-Skyline County ParkSanta Clara414Transient non-communityGroundwater
34Thousand Trails - Morgan HillSanta Clara413CommunityGroundwater
35Monterey MushroomsSanta Clara361Non-transient non-communityGroundwater
36Chemeketa Park Mutual Water CompanySanta Clara346CommunitySurface water
37Aldercroft Heights County Water DistrictSanta Clara338CommunitySurface water
38Joseph Grant County ParkSanta Clara322Transient non-communityGroundwater
39Twin Valley Inc.Santa Clara317CommunityGroundwater
40New Avenue Mutual Water CompanySanta Clara305CommunityGroundwater
41Mt. Pleasant Water Users AssociationSanta Clara300CommunityPurchased surface water
42Lupin LodgeSanta Clara300CommunitySurface water
43Lick Observatory-UcscSanta Clara284CommunitySurface water
44Walden WestSanta Clara273Transient non-communityGroundwater
45Willow Heights MansionSanta Clara269Transient non-communityGroundwater
46Nestldown RanchSanta Clara265Transient non-communityGroundwater
47Saratoga Heights Mutual Water CompanySanta Clara258CommunityPurchased surface water
48Parkway Lakes Rv ParkSanta Clara250CommunityGroundwater
49Casa De Fruta Water SystemSanta Clara250CommunityGroundwater
50George Chiala Farms Inc.Santa Clara250Non-transient non-communityGroundwater

All other water systems in Santa Clara County (70)

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

Santa Clara County water systems: frequently asked questions

How many public water systems are in Santa Clara County, California?

EPA's SDWIS records file 121 active public water systems under Santa Clara County, California: 74 community systems (61%), 22 non-transient non-community systems (18%) and 25 transient non-community systems (21%).

Who supplies drinking water in Santa Clara County, CA?

The largest community water systems filed under Santa Clara County are San Jose Water (1,039,920 people served), City of Sunnyvale (157,566 people served) and City of Santa Clara (130,746 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 Santa Clara County's drinking water come from groundwater or surface water?

Of the 121 active public water systems in Santa Clara County, 68% draw mainly on groundwater and 31% on surface water, counting purchased supplies. The largest system, San Jose Water, uses surface water.

Where can I find a water quality report for Santa Clara 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. 74 community systems are filed under Santa Clara 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 Santa Clara 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 Santa Clara County, California”, https://aquacensus.com/water-systems/california/santa-clara (data as of October 1, 2026).