Public water system · CA4901221
ActiveGraton Mutual Water System
At a glance
Graton Mutual Water System (PWSID CA4901221) is an active community water system in Sonoma County, California. It reports serving 50 people through 16 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. EPA's records list 7 violations for this system; 2 are health-based, and the most recent began in January 2006.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
50
Service connections
16
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Graton Mutual Water System compare with other water systems in Sonoma County?
By EPA's size categories, Graton Mutual Water System is a very small system (500 people or fewer). Sonoma County has 441 active public water systems. Its population served is well below the county average of 1,092 people per system, and accounts for less than 0.1% of the 481,435 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 Graton Mutual Water System 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. 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 Graton Mutual Water System?
EPA lists Graton Mutual Water System 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. 371 of the 441 active systems in Sonoma County (84%) are also privately owned.
Does Graton Mutual Water System have drinking water violations?
EPA's records list 7 violations for this system; 2 are health-based, and the most recent began in January 2006. The violations listed here began between April 1999 and January 2006. By type: 5 monitoring and reporting and 2 contaminant level above the legal limit. The contaminant or rule involved most often is Total coliform bacteria (TCR) (3 of them). EPA lists 7 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 |
|---|---|---|---|---|
| 2006-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Benzenecode 2990 | No | Resolved |
| 2006-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Atrazinecode 2050 | No | Resolved |
| 2006-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitritecode 1041 | No | Resolved |
| 2006-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2003-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2000-09-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 1999-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
All 7 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.
Graton Mutual Water System: frequently asked questions
Who runs Graton Mutual Water System?
Graton Mutual Water System (PWSID CA4901221) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Graton Mutual Water System serve?
Graton Mutual Water System reports serving 50 people through 16 service connections in Sonoma County, California.
Where does Graton Mutual Water System 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 Graton Mutual Water System have any drinking water violations?
EPA's records list 7 violations for this system; 2 are health-based, and the most recent began in January 2006. 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 Graton Mutual Water System'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 7 violations for this system; 2 are health-based, and the most recent began in January 2006. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Graton Mutual Water System's water quality report?
As a community water system, Graton Mutual Water System 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 Sonoma County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Santa Rosa, City of | Sonoma | 175,396 | Community | Groundwater |
| Petaluma, City of | Sonoma | 60,781 | Community | Groundwater |
| Rohnert Park, City of | Sonoma | 43,821 | Community | Groundwater |
| Windsor, Town of | Sonoma | 25,561 | Community | Groundwater |
| Valley of the Moon Water District | Sonoma | 23,107 | Community | Groundwater |
| Sonoma, City of | Sonoma | 11,725 | Community | Groundwater |
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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, “Graton Mutual Water System, PWSID CA4901221, California”, https://aquacensus.com/water-systems/california/graton-mutual-water-system-ca4901221 (data as of October 1, 2026).