Public water system · AZ0410968
ActiveRio Mercado Water
At a glance
Rio Mercado Water (PWSID AZ0410968) is an active community water system in Pima County, Arizona. It reports serving 266 people through 89 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. EPA's records list 10 violations for this system; 1 is health-based, and the most recent began in January 2026.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
266
Service connections
89
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Rio Mercado Water compare with other water systems in Pima County?
By EPA's size categories, Rio Mercado Water is a very small system (500 people or fewer). Pima County has 193 active public water systems. Its population served is well below the county average of 5,896 people per system, and accounts for less than 0.1% of the 1,137,975 people reported by systems filed under the county. Across Arizona, the 1,769 active systems average 4,369 people each. Nationally, the average active community water system reports serving 6,703 people, so Rio Mercado 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. Arizona has 936 active community water systems, 53% of the state's 1,769 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 1,612 Arizona systems (91%) list groundwater as their primary source.
Who owns and regulates Rio Mercado Water?
EPA lists Rio Mercado Water as privately owned. The AZ state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 76 of the 193 active systems in Pima County (39%) are also privately owned.
Does Rio Mercado Water have drinking water violations?
EPA's records list 10 violations for this system; 1 is health-based, and the most recent began in January 2026. The violations listed here began between August 2024 and January 2026. By type: 5 monitoring and reporting, 3 monitoring, 1 required treatment not met and 1 reporting. The contaminant or rule involved most often is Lead and Copper Rule (3 of them). EPA lists 6 as resolved, 2 as unaddressed and 2 as archived. 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. Unaddressed means the violation is not resolved or archived and is not yet covered by formal enforcement. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2026-01-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | No | Unaddressed |
| 2025-07-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | No | Unaddressed |
| 2025-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Fluoridecode 1025 | No | Archived |
| 2025-01-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2025-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Arseniccode 1005 | No | Archived |
| 2024-10-17 | Required treatment not metLSL Inventory · code 2E | Lead and Copper Rule Revisionscode 5200 | Yes | Resolved |
| 2024-10-17 | ReportingLSL Reporting · code 4G | Lead and Copper Rule Revisionscode 5200 | No | Resolved |
| 2024-10-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-09-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-08-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
All 10 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.
Rio Mercado Water: frequently asked questions
Who runs Rio Mercado Water?
Rio Mercado Water (PWSID AZ0410968) is a community water system privately owned. It is regulated by the AZ state drinking water program.
How many people does Rio Mercado Water serve?
Rio Mercado Water reports serving 266 people through 89 service connections in Pima County, Arizona.
Where does Rio Mercado 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 Rio Mercado Water have any drinking water violations?
EPA's records list 10 violations for this system; 1 is health-based, and the most recent began in January 2026. 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 Rio Mercado 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 10 violations for this system; 1 is health-based, and the most recent began in January 2026. For current results, consult the system's annual water quality report, EPA ECHO, or the AZ state drinking water program.
Where can I find Rio Mercado Water's water quality report?
As a community water system, Rio Mercado 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 Pima County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Tucson City of | Pima | 732,906 | Community | Groundwater |
| University of Arizona | Pima | 50,000 | Non-transient non-community | Groundwater |
| Metropolitan Dwid | Pima | 45,570 | Community | Groundwater |
| Oro Valley Water Utility | Pima | 42,316 | Community | Groundwater |
| Community Wc of Green Valley | Pima | 22,085 | Community | Groundwater |
| Usaf Davis Monthan Afb | Pima | 18,640 | 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, “Rio Mercado Water, PWSID AZ0410968, Arizona”, https://aquacensus.com/water-systems/arizona/rio-mercado-water-az0410968 (data as of October 1, 2026).