Public water system · MI0000220

Active

Ann Arbor

At a glance

Ann Arbor (PWSID MI0000220) is an active community water system in Washtenaw County, Michigan. It reports serving 123,851 people through 26,050 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in November 2016.

Dataset updated October 2026 . Source: EPA SDWIS/ECHO public records.

Population served

123,851

Service connections

26,050

Primary source

Surface water

System type

CWS

Community water system

System record

PWSIDMI0000220

System typeCommunity water system

Activity statusActive

Population served123,851

Service connections26,050

Primary water sourceSurface water

Owner typeLocal government

Primacy agencyMI state drinking water program

City servedAnn Arbor

StateMichigan

ZIP—

CountyWashtenaw County

How does Ann Arbor compare with other water systems in Washtenaw County?

By EPA's size categories, Ann Arbor is a very large system (more than 100,000 people). Washtenaw County has 262 active public water systems, and Ann Arbor is the largest of them by population served. Its population served is about 108 times the county average of 1,147 people per system, and accounts for 41% of the 300,406 people reported by systems filed under the county. Across Michigan, the 10,599 active systems average 847 people each. Nationally, the average active community water system reports serving 6,703 people, so Ann Arbor is about 18 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. Michigan has 1,332 active community water systems, 13% of the state's 10,599 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 68 Michigan systems (0.6%) list surface water as their primary source.

Who owns and regulates Ann Arbor?

EPA lists Ann Arbor as owned by a local government. The MI state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 16 of the 262 active systems in Washtenaw County (6.1%) are also owned by a local government.

Does Ann Arbor have drinking water violations?

Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in November 2016. The violations listed here began between July 2002 and November 2016. By type: 9 monitoring and reporting and 3 required treatment not met. The contaminant or rule involved most often is Interim Enhanced Surface Water Treatment Rule (6 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
2016-11-01	Monitoring and reportingMonitoring, Source Water (LT2) · code 32	Cryptosporidiumcode 3015	No	Resolved
2011-01-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Carbon, totalcode 2920	No	Resolved
2008-01-01	Monitoring and reportingMonitoring, Regular · code 03	Endothallcode 2033	No	Resolved
2008-01-01	Required treatment not metSingle Turbidity Exceed (Enhanced SWTR) · code 43	Interim Enhanced Surface Water Treatment Rulecode 0300	Yes	Resolved
2006-07-01	Required treatment not metSingle Turbidity Exceed (Enhanced SWTR) · code 43	Interim Enhanced Surface Water Treatment Rulecode 0300	Yes	Resolved
2006-06-01	Required treatment not metSingle Turbidity Exceed (Enhanced SWTR) · code 43	Interim Enhanced Surface Water Treatment Rulecode 0300	Yes	Resolved
2005-09-01	Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38	Interim Enhanced Surface Water Treatment Rulecode 0300	No	Resolved
2004-07-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Bromatecode 1011	No	Resolved
2003-09-01	Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38	Interim Enhanced Surface Water Treatment Rulecode 0300	No	Resolved
2003-08-01	Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38	Interim Enhanced Surface Water Treatment Rulecode 0300	No	Resolved
2003-04-01	Monitoring and reportingMonitoring, Repeat Major (TCR) · code 25	Total coliform bacteria (TCR)code 3100	No	Resolved
2002-07-01	Monitoring and reportingMonitoring, Repeat Minor (TCR) · code 26	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.

Ann Arbor: frequently asked questions

Who runs Ann Arbor?

Ann Arbor (PWSID MI0000220) is a community water system owned by a local government. It is regulated by the MI state drinking water program.

How many people does Ann Arbor serve?

Ann Arbor reports serving 123,851 people through 26,050 service connections in Washtenaw County, Michigan.

Where does Ann Arbor 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 Ann Arbor have any drinking water violations?

Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in November 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 Ann Arbor'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, 3 are health-based, and the most recent began in November 2016. For current results, consult the system's annual water quality report, EPA ECHO, or the MI state drinking water program.

Where can I find Ann Arbor's water quality report?

As a community water system, Ann Arbor 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 Washtenaw County

Water system	County	Population served	Type	Source
Ypsilanti Community Utility Authority	Washtenaw	53,988	Community	Purchased surface water
Pittsfield Township	Washtenaw	24,500	Community	Purchased surface water
Saline	Washtenaw	9,158	Community	Groundwater
Scio Township	Washtenaw	8,500	Community	Purchased surface water
Milan	Washtenaw	7,363	Community	Groundwater
Superior Township	Washtenaw	6,830	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, “Ann Arbor, PWSID MI0000220, Michigan”, https://aquacensus.com/water-systems/michigan/ann-arbor-mi0000220 (data as of October 1, 2026).