Public water system · CA4110016
ActiveTown of Hillsborough
At a glance
Town of Hillsborough (PWSID CA4110016) is an active community water system in San Mateo County, California. It reports serving 11,766 people through 4,303 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in May 2014.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
11,766
Service connections
4,303
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Town of Hillsborough compare with other water systems in San Mateo County?
By EPA's size categories, Town of Hillsborough is a large system (10,001 to 100,000 people). San Mateo County has 51 active public water systems. Its population served is about 23% below the county average of 15,363 people per system, and accounts for 1.5% of the 783,522 people reported by systems filed under the county. Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so Town of Hillsborough is about 76% above that figure.
What does “community water system” mean?
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. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 506 California systems (6.8%) list purchased surface water as their primary source.
Who owns and regulates Town of Hillsborough?
EPA lists Town of Hillsborough as owned by a local government. The CA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 19 of the 51 active systems in San Mateo County (37%) are also owned by a local government.
Does Town of Hillsborough have drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in May 2014. The violations listed here began between June 1992 and May 2014. By type: 1 contaminant level above the legal limit and 1 monitoring and reporting. The contaminant or rule involved most often is Total coliform bacteria (TCR) (2 of them). EPA lists 2 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2014-05-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 1992-06-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
All 2 violations in EPA's records, newest first. Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Town of Hillsborough: frequently asked questions
Who runs Town of Hillsborough?
Town of Hillsborough (PWSID CA4110016) is a community water system owned by a local government. It is regulated by the CA state drinking water program.
How many people does Town of Hillsborough serve?
Town of Hillsborough reports serving 11,766 people through 4,303 service connections in San Mateo County, California.
Where does Town of Hillsborough get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Town of Hillsborough have any drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in May 2014. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Town of Hillsborough's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in May 2014. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Town of Hillsborough's water quality report?
As a community water system, Town of Hillsborough must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in San Mateo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| City of Daly City | San Mateo | 104,901 | Community | Purchased surface water |
| California Water Service - San Mateo | San Mateo | 102,348 | Community | Purchased surface water |
| City of Redwood City | San Mateo | 92,819 | Community | Purchased surface water |
| California Water Service-S San Francisco | San Mateo | 64,146 | Community | Purchased surface water |
| California Water Service - Bear Gulch | San Mateo | 61,431 | Community | Surface water |
| City of San Bruno | San Mateo | 42,631 | Community | Purchased surface water |
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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, “Town of Hillsborough, PWSID CA4110016, California”, https://aquacensus.com/water-systems/california/town-of-hillsborough-ca4110016 (data as of October 1, 2026).