Public water system · CA4100566
ActiveSan Gregorio Company
At a glance
San Gregorio Company (PWSID CA4100566) is an active transient non-community water system in San Mateo County, California. It reports serving 32 people through 4 service connections. Its primary water source is groundwater under influence of surface water, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in February 2024.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
32
Service connections
4
Primary source
GU
Groundwater under influence of surface water
System type
TNCWS
Transient non-community water system
System record
How does San Gregorio Company compare with other water systems in San Mateo County?
By EPA's size categories, San Gregorio Company is a very small system (500 people or fewer). San Mateo County has 51 active public water systems. Its population served is well below the county average of 15,363 people per system, and accounts for less than 0.1% of the 783,522 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 San Gregorio Company is well 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 under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules. 105 California systems (1.4%) list groundwater under influence of surface water as their primary source.
Who owns and regulates San Gregorio Company?
EPA lists San Gregorio 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. 27 of the 51 active systems in San Mateo County (53%) are also privately owned.
Does San Gregorio Company have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in February 2024. The violations listed here began between July 1996 and February 2024. By type: 9 monitoring and reporting and 3 monitoring. The contaminant or rule involved most often is E. coli (7 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 |
|---|---|---|---|---|
| 2024-02-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2023-01-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-12-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-11-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-10-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-09-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-08-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-07-01 | Monitoring and reportingMonitoring, Source Water (LT2) · code 32 | E. colicode 3014 | No | Resolved |
| 2022-01-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2021-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2016-07-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 1996-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | 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.
San Gregorio Company: frequently asked questions
Who runs San Gregorio Company?
San Gregorio Company (PWSID CA4100566) is a transient non-community water system privately owned. It is regulated by the CA state drinking water program.
How many people does San Gregorio Company serve?
San Gregorio Company reports serving 32 people through 4 service connections in San Mateo County, California.
Where does San Gregorio Company get its water?
EPA SDWIS lists this system's primary water source as groundwater under influence of surface water. Groundwater under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules.
Does San Gregorio Company have any drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in February 2024. 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 San Gregorio 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, none is health-based, and the most recent began in February 2024. For current results, consult EPA ECHO, or the CA state drinking water program.
Where can I find San Gregorio Company's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. San Gregorio Company 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 San Mateo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| City of Daly City | San Mateo | 104,901 | Community | Purchased surface water |
| California Water Service - San Mateo | San Mateo | 102,348 | Community | Purchased surface water |
| City of Redwood City | San Mateo | 92,819 | Community | Purchased surface water |
| California Water Service-S San Francisco | San Mateo | 64,146 | Community | Purchased surface water |
| California Water Service - Bear Gulch | San Mateo | 61,431 | Community | Surface water |
| City of San Bruno | San Mateo | 42,631 | 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, “San Gregorio Company, PWSID CA4100566, California”, https://aquacensus.com/water-systems/california/san-gregorio-company-ca4100566 (data as of October 1, 2026).