Public water system · CA3910027
ActiveCity of Mountain House
At a glance
City of Mountain House (PWSID CA3910027) is an active community water system in San Joaquin County, California. It reports serving 24,948 people through 7,559 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 2010.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
24,948
Service connections
7,559
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does City of Mountain House compare with other water systems in San Joaquin County?
By EPA's size categories, City of Mountain House is a large system (10,001 to 100,000 people). San Joaquin County has 302 active public water systems. Its population served is about 9.7 times the county average of 2,571 people per system, and accounts for 3.2% of the 776,334 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 City of Mountain House is about 3.7 times 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 City of Mountain House?
EPA lists City of Mountain House as owned by a local government. 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. 69 of the 302 active systems in San Joaquin County (23%) are also owned by a local government.
Does City of Mountain House have drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 2010. The violations listed here began between January 2005 and February 2010. By type: 1 monitoring and reporting and 1 contaminant level above the legal limit. The contaminants or rules involved are Total coliform bacteria (TCR) and Total trihalomethanes (TTHM). EPA lists 2 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 |
|---|---|---|---|---|
| 2010-02-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
All 2 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.
City of Mountain House: frequently asked questions
Who runs City of Mountain House?
City of Mountain House (PWSID CA3910027) is a community water system owned by a local government. It is regulated by the CA state drinking water program.
How many people does City of Mountain House serve?
City of Mountain House reports serving 24,948 people through 7,559 service connections in San Joaquin County, California.
Where does City of Mountain House 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 City of Mountain House have any drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in February 2010. 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 City of Mountain House'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 2 violations for this system; 1 is health-based, and the most recent began in February 2010. For current results, consult the system's annual water quality report, EPA ECHO, or the CA state drinking water program.
Where can I find City of Mountain House's water quality report?
As a community water system, City of Mountain House 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 Joaquin County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| City of Stockton | San Joaquin | 191,302 | Community | Surface water |
| California Water Service - Stockton | San Joaquin | 176,266 | Community | Purchased surface water |
| Tracy, City of | San Joaquin | 96,609 | Community | Surface water |
| Manteca, City of | San Joaquin | 84,928 | Community | Purchased surface water |
| Lodi, City of | San Joaquin | 68,272 | Community | Surface water |
| City of Lathrop | San Joaquin | 35,080 | 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, “City of Mountain House, PWSID CA3910027, California”, https://aquacensus.com/water-systems/california/city-of-mountain-house-ca3910027 (data as of October 1, 2026).