Public water system · SD4600291

Active

Selby

At a glance

Selby (PWSID SD4600291) is an active community water system in Walworth County, South Dakota. It reports serving 645 people through 367 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in October 2025.

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

Population served

645

Service connections

367

Primary source

SWP

Purchased surface water

System type

CWS

Community water system

System record

PWSIDSD4600291

System typeCommunity water system

Activity statusActive

Population served645

Service connections367

Primary water sourcePurchased surface water

Owner typeLocal government

Primacy agencySD state drinking water program

City servedSelby

StateSouth Dakota

ZIP57472

CountyWalworth County

How does Selby compare with other water systems in Walworth County?

By EPA's size categories, Selby is a small system (501 to 3,300 people). Walworth County has 4 active public water systems, and Selby is the 3rd-largest of them by population served. Its population served is well below the county average of 6,194 people per system, and accounts for 2.6% of the 24,777 people reported by systems filed under the county. Across South Dakota, the 699 active systems average 1,387 people each. Nationally, the average active community water system reports serving 6,703 people, so Selby 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. South Dakota has 510 active community water systems, 73% of the state's 699 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 142 South Dakota systems (20%) list purchased surface water as their primary source.

Who owns and regulates Selby?

EPA lists Selby as owned by a local government. The SD state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 3 of the 4 active systems in Walworth County (75%) are also owned by a local government.

Does Selby have drinking water violations?

Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in October 2025. The violations listed here began between August 2015 and October 2025. By type: 8 monitoring and reporting, 2 monitoring and 2 required treatment not met. The contaminant or rule involved most often is Chlorine (3 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
2025-10-01	MonitoringMonitoring, Routine (RTCR) · code 3A	Revised Total Coliform Rulecode 8000	No	Resolved
2023-12-01	MonitoringMonitoring, Routine (RTCR) · code 3A	Revised Total Coliform Rulecode 8000	No	Resolved
2023-10-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Chlorinecode 0999	No	Resolved
2021-10-01	Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52	Lead and Copper Rulecode 5000	No	Resolved
2019-08-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Total trihalomethanes (TTHM)code 2950	No	Resolved
2019-08-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Haloacetic acids (HAA5)code 2456	No	Resolved
2019-02-12	Required treatment not metFailure To Address Deficiency · code 45	Long Term 2 Enhanced Surface Water Treatment Rulecode 0800	Yes	Resolved
2017-04-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Chlorinecode 0999	No	Resolved
2016-01-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Chlorinecode 0999	No	Resolved
2015-11-15	Required treatment not metTreatment Technique No Certif. Operator · code 12	Stage 1 Disinfectants and Disinfection Byproducts Rulecode 0400	Yes	Resolved
2015-08-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Haloacetic acids (HAA5)code 2456	No	Resolved
2015-08-01	Monitoring and reportingMonitoring and Reporting (DBP) · code 27	Total trihalomethanes (TTHM)code 2950	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.

Selby: frequently asked questions

Who runs Selby?

Selby (PWSID SD4600291) is a community water system owned by a local government. It is regulated by the SD state drinking water program.

How many people does Selby serve?

Selby reports serving 645 people through 367 service connections in Walworth County, South Dakota.

Where does Selby get its water?

EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.

Does Selby have any drinking water violations?

Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in October 2025. 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 Selby'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, 2 are health-based, and the most recent began in October 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the SD state drinking water program.

Where can I find Selby's water quality report?

As a community water system, Selby 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 Walworth County

Water system	County	Population served	Type	Source
Web Water Development Association	Walworth + 9 more	20,750	Community	Surface water
Mobridge	Walworth	3,261	Community	Surface water
Java	Walworth	121	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, “Selby, PWSID SD4600291, South Dakota”, https://aquacensus.com/water-systems/south-dakota/selby-sd4600291 (data as of October 1, 2026).