Public water system · CA4310001
ActiveCwsc Los Altos Suburban
At a glance
Cwsc Los Altos Suburban (PWSID CA4310001) is an active community water system in Santa Clara County, California. It reports serving 69,973 people through 18,530 service connections. Its primary water source is purchased surface water, and EPA lists it as privately owned. EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in January 2002.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
69,973
Service connections
18,530
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Cwsc Los Altos Suburban compare with other water systems in Santa Clara County?
By EPA's size categories, Cwsc Los Altos Suburban is a large system (10,001 to 100,000 people). Santa Clara County has 121 active public water systems. Its population served is about 4 times the county average of 17,334 people per system, and accounts for 3.3% of the 2,097,447 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 Cwsc Los Altos Suburban is about 10 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 Cwsc Los Altos Suburban?
EPA lists Cwsc Los Altos Suburban 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. 82 of the 121 active systems in Santa Clara County (68%) are also privately owned.
Does Cwsc Los Altos Suburban have drinking water violations?
EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in January 2002. The violations listed here began between November 1992 and January 2002. By type: 2 monitoring and reporting and 1 contaminant level above the legal limit. The contaminants or rules involved are Simazine, Nitrate and Total coliform bacteria (TCR). EPA lists 3 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 |
|---|---|---|---|---|
| 2002-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Simazinecode 2037 | No | Resolved |
| 1995-03-29 | Monitoring and reportingMonitoring, Check/Repeat/Confirmation · code 04 | Nitratecode 1040 | No | Resolved |
| 1992-11-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Acute (TCR) · code 21 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
All 3 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.
Cwsc Los Altos Suburban: frequently asked questions
Who runs Cwsc Los Altos Suburban?
Cwsc Los Altos Suburban (PWSID CA4310001) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Cwsc Los Altos Suburban serve?
Cwsc Los Altos Suburban reports serving 69,973 people through 18,530 service connections in Santa Clara County, California.
Where does Cwsc Los Altos Suburban 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 Cwsc Los Altos Suburban have any drinking water violations?
EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in January 2002. 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 Cwsc Los Altos Suburban'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 3 violations for this system; 1 is health-based, and the most recent began in January 2002. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Cwsc Los Altos Suburban's water quality report?
As a community water system, Cwsc Los Altos Suburban 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 Santa Clara County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| San Jose Water | Santa Clara | 1,039,920 | Community | Surface water |
| City of Sunnyvale | Santa Clara | 157,566 | Community | Purchased surface water |
| City of Santa Clara | Santa Clara | 130,746 | Community | Purchased surface water |
| Great Oaks Wc Inc. | Santa Clara | 110,088 | Community | Groundwater |
| City of San Jose - Evg/Edv/Coy | Santa Clara | 101,265 | Community | Purchased surface water |
| City of Milpitas | Santa Clara | 81,773 | 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, “Cwsc Los Altos Suburban, PWSID CA4310001, California”, https://aquacensus.com/water-systems/california/cwsc-los-altos-suburban-ca4310001 (data as of October 1, 2026).