Public water system · CA2800521
ActiveCircle Oaks Water District
At a glance
Circle Oaks Water District (PWSID CA2800521) is an active community water system in Napa County, California. It reports serving 500 people through 190 service connections. Its primary water source is surface water, and EPA lists it as privately owned. EPA's records list 5 violations for this system; none is health-based, and the most recent began in January 2020.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
500
Service connections
190
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Circle Oaks Water District compare with other water systems in Napa County?
By EPA's size categories, Circle Oaks Water District is a very small system (500 people or fewer). Napa County has 188 active public water systems. Its population served is about 42% below the county average of 861 people per system, and accounts for 0.3% of the 161,950 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 Circle Oaks Water District is well below 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. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 609 California systems (8.1%) list surface water as their primary source.
Who owns and regulates Circle Oaks Water District?
EPA lists Circle Oaks Water District 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. 168 of the 188 active systems in Napa County (89%) are also privately owned.
Does Circle Oaks Water District have drinking water violations?
EPA's records list 5 violations for this system; none is health-based, and the most recent began in January 2020. The violations listed here began between October 1980 and January 2020. By type: 5 monitoring and reporting. The contaminant or rule involved most often is Gross alpha (excluding radon and uranium) (2 of them). EPA lists 3 as resolved and 2 as archived. 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. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2020-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2006-12-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1993-07-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | No | Resolved |
| 1981-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Archived |
| 1980-10-30 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Archived |
All 5 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.
Circle Oaks Water District: frequently asked questions
Who runs Circle Oaks Water District?
Circle Oaks Water District (PWSID CA2800521) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Circle Oaks Water District serve?
Circle Oaks Water District reports serving 500 people through 190 service connections in Napa County, California.
Where does Circle Oaks Water District get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Circle Oaks Water District have any drinking water violations?
EPA's records list 5 violations for this system; none is health-based, and the most recent began in January 2020. 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 Circle Oaks Water District'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 5 violations for this system; none is health-based, and the most recent began in January 2020. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Circle Oaks Water District's water quality report?
As a community water system, Circle Oaks Water District 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 Napa County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Napa, City of | Napa | 84,804 | Community | Surface water |
| American Canyon, City of | Napa | 21,437 | Community | Surface water |
| Phelps Vineyards | Napa | 19,412 | Non-transient non-community | Groundwater |
| Calistoga, City of | Napa | 5,610 | Community | Surface water |
| St. Helena, City of | Napa | 5,386 | Community | Surface water |
| Town of Yountville | Napa | 2,787 | 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, “Circle Oaks Water District, PWSID CA2800521, California”, https://aquacensus.com/water-systems/california/circle-oaks-water-district-ca2800521 (data as of October 1, 2026).