Public water system · CA4100512
ActiveLoma Mar Mutual
At a glance
Loma Mar Mutual (PWSID CA4100512) is an active community water system in San Mateo County, California. It reports serving 65 people through 34 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, 8 are health-based, and the most recent began in August 2016.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
65
Service connections
34
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Loma Mar Mutual compare with other water systems in San Mateo County?
By EPA's size categories, Loma Mar Mutual 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 community water system reports serving 6,703 people, so Loma Mar Mutual 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 Loma Mar Mutual?
EPA lists Loma Mar Mutual 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 Loma Mar Mutual have drinking water violations?
Of the 12 most recent violations in EPA's records, 8 are health-based, and the most recent began in August 2016. The violations listed here began between April 2003 and August 2016. By type: 6 required treatment not met, 3 monitoring and reporting, 2 contaminant level above the legal limit and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Surface Water Treatment Rule (5 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 |
|---|---|---|---|---|
| 2016-08-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2016-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2014-09-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2013-03-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2006-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-12-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2005-01-01 | Required treatment not metMonthly Turbidity Exceed (Enhanced SWTR) · code 44 | Interim Enhanced Surface Water Treatment Rulecode 0300 | Yes | Resolved |
| 2005-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2004-04-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2003-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2003-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Acute (TCR) · code 21 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2003-04-01 | 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.
Loma Mar Mutual: frequently asked questions
Who runs Loma Mar Mutual?
Loma Mar Mutual (PWSID CA4100512) is a community water system privately owned. It is regulated by the CA state drinking water program.
How many people does Loma Mar Mutual serve?
Loma Mar Mutual reports serving 65 people through 34 service connections in San Mateo County, California.
Where does Loma Mar Mutual 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 Loma Mar Mutual have any drinking water violations?
Of the 12 most recent violations in EPA's records, 8 are health-based, and the most recent began in August 2016. 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 Loma Mar Mutual'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, 8 are health-based, and the most recent began in August 2016. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find Loma Mar Mutual's water quality report?
As a community water system, Loma Mar Mutual 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 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, “Loma Mar Mutual, PWSID CA4100512, California”, https://aquacensus.com/water-systems/california/loma-mar-mutual-ca4100512 (data as of October 1, 2026).