Public water system · CA2810001
ActiveHowell Mountain Mutual Water Company
At a glance
Howell Mountain Mutual Water Company (PWSID CA2810001) is an active community water system in Napa County, California. It reports serving 1,240 people through 379 service connections. Its primary water source is surface water, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in January 2023.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
1,240
Service connections
379
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Howell Mountain Mutual Water Company compare with other water systems in Napa County?
By EPA's size categories, Howell Mountain Mutual Water Company is a small system (501 to 3,300 people). Napa County has 188 active public water systems. Its population served is about 44% above the county average of 861 people per system, and accounts for 0.8% 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 Howell Mountain Mutual Water Company 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 Howell Mountain Mutual Water Company?
EPA lists Howell Mountain Mutual Water Company 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 Howell Mountain Mutual Water Company have drinking water violations?
Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in January 2023. The violations listed here began between October 2010 and January 2023. By type: 10 contaminant level above the legal limit and 2 monitoring and reporting. The contaminant or rule involved most often is Total trihalomethanes (TTHM) (8 of them). EPA lists 12 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 |
|---|---|---|---|---|
| 2023-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2021-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2020-10-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2016-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2016-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2015-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2013-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2013-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2011-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2011-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2011-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2010-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
The 12 most recent 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.
Howell Mountain Mutual Water Company: frequently asked questions
Who runs Howell Mountain Mutual Water Company?
Howell Mountain Mutual Water Company (PWSID CA2810001) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Howell Mountain Mutual Water Company serve?
Howell Mountain Mutual Water Company reports serving 1,240 people through 379 service connections in Napa County, California.
Where does Howell Mountain Mutual Water Company 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 Howell Mountain Mutual Water Company have any drinking water violations?
Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in January 2023. 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 Howell Mountain Mutual Water Company'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. Of the 12 most recent violations in EPA's records, 10 are health-based, and the most recent began in January 2023. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Howell Mountain Mutual Water Company's water quality report?
As a community water system, Howell Mountain Mutual Water Company 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, “Howell Mountain Mutual Water Company, PWSID CA2810001, California”, https://aquacensus.com/water-systems/california/howell-mountain-mutual-water-company-ca2810001 (data as of October 1, 2026).