OK / Duncan
OK · Tap water records
Duncan tap water, in plain English
Here is what the EPA's own data shows about tap water in Duncan. According to EPA SDWIS data retrieved June 2026, Duncan is served by 1 active community water system, together reported to serve about 23,000 people.
As of June 2026, EPA records show 92 violations across the community water system(s) serving Duncan, going back to the earliest EPA record. 64 of these are classified by the EPA as health-based (a contaminant recorded above the limit the EPA tracks); the rest are monitoring or reporting violations. Each is listed by system below, with its status.
What the EPA has on record, by system
Duncan Public Utilities Authority
23,000 served · surface water · PWSID OK1010809 - Health-based CARBON, TOTAL: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 14 times between January 2020 and October 2024. The EPA record for these does not include a measured level. EPA records do not show all of these as returned to compliance.
- Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 39 times between October 2013 and January 2023. The EPA record lists a level of 0.085 MG/L; the limit (MCL) is 0.08 MG/L. EPA records do not show all of these as returned to compliance.
- Health-based Total Haloacetic Acids (HAA5): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 6 times between January 2016 and July 2017. The EPA record lists a level of 0.062 MG/L; the limit (MCL) is 0.06 MG/L. EPA records do not show all of these as returned to compliance.
- Health-based Interim Enhanced Surface Water Treatment Rule: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded once in December 2016. The EPA record for these does not include a measured level. All have since returned to compliance, per EPA records.
- Health-based Coliform (TCR): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 2 times between April 1991 and September 1994. The EPA record lists a level of 0 ; the limit (MCL) is 0 . All have since returned to compliance, per EPA records.
- Health-based Coliform (Pre-TCR): a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 2 times between November 1986 and May 1987. The EPA record lists a level of 23 ; the limit (MCL) is 0 . All have since returned to compliance, per EPA records.
- Monitoring Chloramine: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 7 times between October 2017 and November 2025. EPA records do not show all of these as returned to compliance.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 7 times between July 2023 and November 2024. EPA records do not show all of these as returned to compliance.
- Monitoring CARBON, TOTAL: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 8 times in August 2024. EPA records do not show all of these as returned to compliance.
- Monitoring TTHM: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between November 2016 and February 2017. All have since returned to compliance, per EPA records.
- Monitoring Total Haloacetic Acids (HAA5): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between November 2016 and February 2017. All have since returned to compliance, per EPA records.
- Monitoring Coliform (TCR): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in May 1998. All have since returned to compliance, per EPA records.
- Monitoring Turbidity: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in March 1984. All have since returned to compliance, per EPA records.
What this means
A health-based violation means a contaminant was recorded above the limit the EPA tracks for it. A monitoring or reporting violation means a required test or report was late or missed — not that a contaminant was measured above a limit. “Returned to compliance” means the EPA recorded the issue as resolved.
This page summarizes the EPA's own records and does not assess whether your water is safe to drink. For the most current details, you can verify every record directly with the EPA, and contact your water system with questions.
Source: U.S. EPA Envirofacts SDWIS, retrieved June 2026. Records cover the EPA's full reporting history for these systems. Verify at EPA ECHO.