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
🔒 Create a free account to export CSV| # | Water system | County | Population served | Type | Source |
|---|---|---|---|---|---|
| 1 | East Bay MUD | Alameda | 1,442,800 | Community | Surface water |
| 2 | Alameda County Water District | Alameda | 344,000 | Community | Surface water |
| 3 | City of Hayward | Alameda | 162,954 | Community | Purchased surface water |
| 4 | Dublin San Ramon Services District | Alameda | 98,776 | Community | Purchased surface water |
| 5 | City of Pleasanton | Alameda | 76,689 | Community | Purchased surface water |
| 6 | California Water Service - Livermore | Alameda | 60,414 | Community | Purchased surface water |
| 7 | City of Livermore | Alameda | 38,892 | Community | Purchased surface water |
| 8 | Lawrence Livermore National Lab Site 200 | Alameda | 10,870 | Non-transient non-community | Purchased surface water |
| 9 | Ebrpd - Del Valle Regional Park | Alameda | 9,024 | Transient non-community | Surface water |
| 10 | Chp - Mission Grade Scales | Alameda | 1,800 | Transient non-community | Groundwater |
| 11 | Alameda Point | Alameda | 1,400 | Community | Purchased surface water |
| 12 | Castlewood Domestic Water System | Alameda | 524 | Community | Purchased groundwater |
| 13 | Trailer Haven Mobile Home Park | Alameda | 459 | Community | Purchased surface water |
| 14 | Town of Sunol - Sfpuc | Alameda | 281 | Community | Purchased surface water |
| 15 | Sunol Super Stop | Alameda | 155 | Transient non-community | Groundwater |
| 16 | Ebrpd - Sunol Regional Wilderness | Alameda | 91 | Transient non-community | Groundwater |
| 17 | Usbr-Sldmwa - Cvp Jones Pumping Plant | Alameda | 90 | Non-transient non-community | Surface water |
| 18 | Alameda County Fairgrounds | Alameda | 82 | Non-transient non-community | Groundwater |
| 19 | Purple Orchid Resort Spa | Alameda | 52 | Transient non-community | Groundwater |
| 20 | Norris Canyon Property Owners Assn | Alameda | 50 | Community | Groundwater |
| 21 | Mountain House School | Alameda | 50 | Non-transient non-community | Purchased surface water |
| 22 | Ebrpd - Piedmont Stables | Alameda | 45 | Transient non-community | Groundwater |
| 23 | Zone 7 Water Agency | Alameda | 40 | Community | Surface water |
| 24 | Rancho Los Mochos-Bsa Camp | Alameda | 38 | Transient non-community | Groundwater |
| 25 | Rivers End Marina | Alameda | 32 | Transient non-community | Groundwater |
| 26 | Mountain House Bar | Alameda | 25 | Transient non-community | Groundwater |
| 27 | Sfpuc-Pleasanton Wells | Alameda | 1 | Community | Groundwater |
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
- All California public water systems· 7,479 active
- Glenn County· 34 systems
- Sierra County· 32 systems
- Del Norte County· 31 systems
- Colusa County· 29 systems
- Modoc County· 16 systems
- Harris County· 12 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 Alameda County, California”, https://aquacensus.com/water-systems/california/alameda (data as of October 1, 2026).