MO / Mercer
MO · Tap water records
Mercer tap water, in plain English
Here is what the EPA's own data shows about tap water in Mercer. According to EPA SDWIS data retrieved June 2026, Mercer is served by 2 active community water systems, together reported to serve about 3,518 people.
As of June 2026, EPA records show 52 violations across the community water system(s) serving Mercer, going back to the earliest EPA record. 25 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
Mercer County Pwsd 1
3,200 served · surface water · PWSID MO2024382 - Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 2 times in July 2015. The EPA record lists a level of 83 UG/L; the limit (MCL) is 80 UG/L. All have since returned to compliance, per EPA records.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between March 2025 and March 2025. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 11 times between November 2023 and June 2024. EPA records do not show all of these as returned to compliance.
- Monitoring Consumer Confidence Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in July 2014. All have since returned to compliance, per EPA records.
Mercer Pws
318 served · groundwater · PWSID MO2010515 - Health-based TTHM: a health-based violation (a contaminant recorded above the limit the EPA tracks), recorded 23 times between April 2016 and October 2025. The EPA record lists a level of 82 UG/L; the limit (MCL) is 80 UG/L. 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 4 times in July 2023. EPA records do not show all of these as returned to compliance.
- Monitoring Total Haloacetic Acids (HAA5): a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 4 times in July 2023. EPA records do not show all of these as returned to compliance.
- Monitoring Public Notice: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between February 2021 and April 2021. All have since returned to compliance, per EPA records.
- Monitoring Revised Total Coliform Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded once in October 2020. All have since returned to compliance, per EPA records.
- Monitoring Lead and Copper Rule: a monitoring or reporting violation (a required test or report was late or missed — not a measured exceedance), recorded 2 times between January 1995 and April 2011. 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.