Public water system · CA4000805
ActiveCallender Grove Mutual Water
At a glance
Callender Grove Mutual Water (PWSID CA4000805) is an active community water system in San Luis Obispo County, California. It reports serving 126 people through 37 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. EPA's records list one violation for this system; it is not health-based, and the most recent began in October 2022.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
126
Service connections
37
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Callender Grove Mutual Water compare with other water systems in San Luis Obispo County?
By EPA's size categories, Callender Grove Mutual Water is a very small system (500 people or fewer). San Luis Obispo County has 171 active public water systems. Its population served is well below the county average of 2,038 people per system, and accounts for less than 0.1% of the 348,510 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 Callender Grove Mutual Water 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 Callender Grove Mutual Water?
EPA lists Callender Grove Mutual Water 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. 130 of the 171 active systems in San Luis Obispo County (76%) are also privately owned.
Does Callender Grove Mutual Water have drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in October 2022. By type: 1 monitoring and reporting. The contaminant or rule involved is Lead and Copper Rule. EPA lists 1 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 |
|---|---|---|---|---|
| 2022-10-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
The one violation in EPA's records.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.
Callender Grove Mutual Water: frequently asked questions
Who runs Callender Grove Mutual Water?
Callender Grove Mutual Water (PWSID CA4000805) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Callender Grove Mutual Water serve?
Callender Grove Mutual Water reports serving 126 people through 37 service connections in San Luis Obispo County, California.
Where does Callender Grove Mutual Water 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 Callender Grove Mutual Water have any drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in October 2022. 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 Callender Grove Mutual Water'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 one violation for this system; it is not health-based, and the most recent began in October 2022. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Callender Grove Mutual Water's water quality report?
As a community water system, Callender Grove Mutual Water 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 San Luis Obispo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Santa Margarita Recreation Area | San Luis Obispo | 50,001 | Transient non-community | Groundwater |
| San Luis Obispo Water Department | San Luis Obispo | 47,788 | Community | Surface water |
| City of Paso Robles Water Division | San Luis Obispo | 31,176 | Community | Surface water |
| Atascadero Mutual Water Co | San Luis Obispo | 30,618 | Community | Groundwater |
| City of Arroyo Grande Utilities Division | San Luis Obispo | 17,963 | Community | Purchased surface water |
| California Mens Colony | San Luis Obispo | 15,000 | Community | 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, “Callender Grove Mutual Water, PWSID CA4000805, California”, https://aquacensus.com/water-systems/california/callender-grove-mutual-water-ca4000805 (data as of October 1, 2026).