Public water system · CA1910142
ActiveGswc-San Dimas
At a glance
Gswc-San Dimas (PWSID CA1910142) is an active community water system in Los Angeles County, California. It reports serving 56,538 people through 16,163 service connections. Its primary water source is purchased surface water, and EPA lists it as privately owned. EPA's records list 2 violations for this system; all are health-based, and the most recent began in September 1997.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
56,538
Service connections
16,163
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Gswc-San Dimas compare with other water systems in Los Angeles County?
By EPA's size categories, Gswc-San Dimas is a large system (10,001 to 100,000 people). Los Angeles County has 275 active public water systems. Its population served is about 54% above the county average of 36,762 people per system, and accounts for 0.6% of the 10,109,668 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 Gswc-San Dimas is about 8.4 times 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 Gswc-San Dimas?
EPA lists Gswc-San Dimas as privately owned. 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. 150 of the 275 active systems in Los Angeles County (55%) are also privately owned.
Does Gswc-San Dimas have drinking water violations?
EPA's records list 2 violations for this system; all are health-based, and the most recent began in September 1997. The violations listed here began between December 1995 and September 1997. By type: 2 contaminant level above the legal limit. The contaminant or rule involved most often is Nitrate (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 |
|---|---|---|---|---|
| 1997-09-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Nitratecode 1040 | Yes | Resolved |
| 1995-12-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Nitratecode 1040 | Yes | 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.
Gswc-San Dimas: frequently asked questions
Who runs Gswc-San Dimas?
Gswc-San Dimas (PWSID CA1910142) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Gswc-San Dimas serve?
Gswc-San Dimas reports serving 56,538 people through 16,163 service connections in Los Angeles County, California.
Where does Gswc-San Dimas 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 Gswc-San Dimas have any drinking water violations?
EPA's records list 2 violations for this system; all are health-based, and the most recent began in September 1997. 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 Gswc-San Dimas' 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; all are health-based, and the most recent began in September 1997. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Gswc-San Dimas' water quality report?
As a community water system, Gswc-San Dimas 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 Los Angeles County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Los Angeles-City, Dept. of Water & Power | Los Angeles | 3,875,566 | Community | Surface water |
| Long Beach Utilities Department | Los Angeles | 466,772 | Community | Purchased surface water |
| Santa Clarita Valley Water Agency | Los Angeles | 294,090 | Community | Surface water |
| Gswc - Southwest | Los Angeles | 277,740 | Community | Purchased surface water |
| San Gabriel Valley Water Co.-El Monte | Los Angeles | 248,000 | Community | Groundwater |
| Los Angeles Cwwd 40 Reg 4 & 34 Lancaster | Los Angeles | 208,129 | Community | Purchased surface water |
Related pages
Working with water-system records? Pro adds alerts, change history and CSV export ($49/mo); Enterprise adds full national files, the API and an MCP server for AI tools.
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, “Gswc-San Dimas, PWSID CA1910142, California”, https://aquacensus.com/water-systems/california/gswc-san-dimas-ca1910142 (data as of October 1, 2026).