Public water system · CA5010033
ActiveCity of Modesto - Grayson
At a glance
City of Modesto - Grayson (PWSID CA5010033) is an active community water system in Stanislaus County, California. It reports serving 914 people through 278 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. EPA's records list 6 violations for this system; all are health-based, and the most recent began in June 2003.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
914
Service connections
278
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does City of Modesto - Grayson compare with other water systems in Stanislaus County?
By EPA's size categories, City of Modesto - Grayson is a small system (501 to 3,300 people). Stanislaus County has 191 active public water systems. Its population served is about 66% below the county average of 2,684 people per system, and accounts for 0.2% of the 512,656 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 Modesto - Grayson 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 City of Modesto - Grayson?
EPA lists City of Modesto - Grayson 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. 57 of the 191 active systems in Stanislaus County (30%) are also owned by a local government.
Does City of Modesto - Grayson have drinking water violations?
EPA's records list 6 violations for this system; all are health-based, and the most recent began in June 2003. The violations listed here began between April 1993 and June 2003. By type: 6 contaminant level above the legal limit. The contaminant or rule involved most often is Nitrate (5 of them). EPA lists 6 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 |
|---|---|---|---|---|
| 2003-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Single Sample · code 01 | Nitratecode 1040 | Yes | Resolved |
| 1998-12-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Single Sample · code 01 | Nitratecode 1040 | Yes | Resolved |
| 1997-12-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Single Sample · code 01 | Nitratecode 1040 | Yes | Resolved |
| 1995-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Nitratecode 1040 | Yes | Resolved |
| 1995-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Nitratecode 1040 | Yes | Resolved |
| 1993-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
All 6 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 Modesto - Grayson: frequently asked questions
Who runs City of Modesto - Grayson?
City of Modesto - Grayson (PWSID CA5010033) 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 Modesto - Grayson serve?
City of Modesto - Grayson reports serving 914 people through 278 service connections in Stanislaus County, California.
Where does City of Modesto - Grayson 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 City of Modesto - Grayson have any drinking water violations?
EPA's records list 6 violations for this system; all are health-based, and the most recent began in June 2003. 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 Modesto - Grayson'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 6 violations for this system; all are health-based, and the most recent began in June 2003. 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 Modesto - Grayson's water quality report?
As a community water system, City of Modesto - Grayson 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 Stanislaus County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Modesto, City of | Stanislaus | 218,771 | Community | Purchased surface water |
| Turlock, City of | Stanislaus | 72,682 | Community | Purchased surface water |
| Ceres, City of | Stanislaus | 54,513 | Community | Purchased surface water |
| Patterson, City of | Stanislaus | 24,977 | Community | Groundwater |
| Riverbank, City of | Stanislaus | 24,834 | Community | Groundwater |
| Oakdale, City of | Stanislaus | 23,235 | 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, “City of Modesto - Grayson, PWSID CA5010033, California”, https://aquacensus.com/water-systems/california/city-of-modesto-grayson-ca5010033 (data as of October 1, 2026).