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Alameda County, California — public water systems

At a glance

27 active public water systems are filed under Alameda County, California in EPA's SDWIS records, together reporting 2,249,634 people served. The largest is East Bay MUD, which reports serving 1,442,800 people. 14 are community water systems serving people where they live; the other 13 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

27

Population served

2.2M

Community systems

14

Groundwater share

44.4%

How does Alameda County compare with other California counties?

Alameda County has the 56th-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 2,249,634 people served in total, the 6th-largest county figure in the state and 5.3% of the statewide total. The average system here reports serving 83,320 people, about 15 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 Alameda County's drinking water come from?

By primary water source, Alameda County's active systems draw on groundwater (11, 41%), purchased surface water (10, 37%), surface water (5, 19%) and purchased groundwater (1, 3.7%). Overall, 44% rely mainly on groundwater (including purchased groundwater) and 56% 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, East Bay MUD, draws primarily on surface water.

What kinds of water systems operate in Alameda County?

Alameda County's active systems break down as 14 community systems (52%), 4 non-transient non-community systems (15%) and 9 transient non-community systems (33%). 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 local government (56%), private (30%), federal government (7.4%) and public/private partnership (3.7%).

Water systems in Alameda County

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Active public water systems in Alameda County, California
#Water systemCountyPopulation servedTypeSource
1East Bay MUDAlameda1,442,800CommunitySurface water
2Alameda County Water DistrictAlameda344,000CommunitySurface water
3City of HaywardAlameda162,954CommunityPurchased surface water
4Dublin San Ramon Services DistrictAlameda98,776CommunityPurchased surface water
5City of PleasantonAlameda76,689CommunityPurchased surface water
6California Water Service - LivermoreAlameda60,414CommunityPurchased surface water
7City of LivermoreAlameda38,892CommunityPurchased surface water
8Lawrence Livermore National Lab Site 200Alameda10,870Non-transient non-communityPurchased surface water
9Ebrpd - Del Valle Regional ParkAlameda9,024Transient non-communitySurface water
10Chp - Mission Grade ScalesAlameda1,800Transient non-communityGroundwater
11Alameda PointAlameda1,400CommunityPurchased surface water
12Castlewood Domestic Water SystemAlameda524CommunityPurchased groundwater
13Trailer Haven Mobile Home ParkAlameda459CommunityPurchased surface water
14Town of Sunol - SfpucAlameda281CommunityPurchased surface water
15Sunol Super StopAlameda155Transient non-communityGroundwater
16Ebrpd - Sunol Regional WildernessAlameda91Transient non-communityGroundwater
17Usbr-Sldmwa - Cvp Jones Pumping PlantAlameda90Non-transient non-communitySurface water
18Alameda County FairgroundsAlameda82Non-transient non-communityGroundwater
19Purple Orchid Resort SpaAlameda52Transient non-communityGroundwater
20Norris Canyon Property Owners AssnAlameda50CommunityGroundwater
21Mountain House SchoolAlameda50Non-transient non-communityPurchased surface water
22Ebrpd - Piedmont StablesAlameda45Transient non-communityGroundwater
23Zone 7 Water AgencyAlameda40CommunitySurface water
24Rancho Los Mochos-Bsa CampAlameda38Transient non-communityGroundwater
25Rivers End MarinaAlameda32Transient non-communityGroundwater
26Mountain House BarAlameda25Transient non-communityGroundwater
27Sfpuc-Pleasanton WellsAlameda1CommunityGroundwater

Alameda County water systems: frequently asked questions

How many public water systems are in Alameda County, California?

EPA's SDWIS records file 27 active public water systems under Alameda County, California: 14 community systems (52%), 4 non-transient non-community systems (15%) and 9 transient non-community systems (33%).

Who supplies drinking water in Alameda County, CA?

The largest community water systems filed under Alameda County are East Bay MUD (1,442,800 people served), Alameda County Water District (344,000 people served) and City of Hayward (162,954 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 Alameda County's drinking water come from groundwater or surface water?

Of the 27 active public water systems in Alameda County, 44% draw mainly on groundwater and 56% on surface water, counting purchased supplies. The largest system, East Bay MUD, uses surface water.

Where can I find a water quality report for Alameda 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. 14 community systems are filed under Alameda 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 Alameda 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 Alameda County, California”, https://aquacensus.com/water-systems/california/alameda (data as of October 1, 2026).