Public water system · CA2800740
ActiveMont St. John Cellars
At a glance
Mont St. John Cellars (PWSID CA2800740) is an active transient non-community water system in Napa County, California. It reports serving 100 people through 1 service connection. Its primary water source is groundwater, and EPA lists it as privately owned. EPA's records list 6 violations for this system; none is health-based, and the most recent began in April 2015.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
100
Service connections
1
Primary source
GW
Groundwater
System type
TNCWS
Transient non-community water system
System record
How does Mont St. John Cellars compare with other water systems in Napa County?
By EPA's size categories, Mont St. John Cellars is a very small system (500 people or fewer). Napa County has 188 active public water systems. Its population served is well below the county average of 861 people per system, and accounts for less than 0.1% 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 transient non-community water system reports serving 144 people, so Mont St. John Cellars is about 31% below that figure.
What does “transient non-community water system” mean?
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. California has 3,016 active transient non-community water systems, 40% of the state's 7,479 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 6,179 California systems (83%) list groundwater as their primary source.
Who owns and regulates Mont St. John Cellars?
EPA lists Mont St. John Cellars 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 Mont St. John Cellars have drinking water violations?
EPA's records list 6 violations for this system; none is health-based, and the most recent began in April 2015. The violations listed here began between September 1984 and April 2015. By type: 5 monitoring and reporting and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Total coliform bacteria (TCR) (5 of them). EPA lists 5 as resolved and 1 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 |
|---|---|---|---|---|
| 2015-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2014-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2013-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2011-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1984-09-01 | Public notice, recordkeeping or otherNotification, Public · code 06 | Not reported | No | Archived |
All 6 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.
Mont St. John Cellars: frequently asked questions
Who runs Mont St. John Cellars?
Mont St. John Cellars (PWSID CA2800740) is a transient non-community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Mont St. John Cellars serve?
Mont St. John Cellars reports serving 100 people through 1 service connection in Napa County, California.
Where does Mont St. John Cellars get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Mont St. John Cellars have any drinking water violations?
EPA's records list 6 violations for this system; none is health-based, and the most recent began in April 2015. 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 Mont St. John Cellars' 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 6 violations for this system; none is health-based, and the most recent began in April 2015. For current results, consult EPA ECHO, or the CA state drinking water program.
Where can I find Mont St. John Cellars' water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Mont St. John Cellars is a transient non-community water system, so it is not required to publish one; like every public water system, it must notify the people it serves about violations under EPA's public notification rules.
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, “Mont St. John Cellars, PWSID CA2800740, California”, https://aquacensus.com/water-systems/california/mont-st-john-cellars-ca2800740 (data as of October 1, 2026).