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Mercer PWS

What EPA’s and CDC’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.

Serves
318 people
Connections
181
Water source
Groundwater bought from another system
Based in
Mercer, MO
County
Mercer
Owner
Local government
The ZIP code it serves

64661

The short answer

1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Total trihalomethanes (TTHM), above the legal limit. 12 health-based violations since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2013 to 2025.

Total trihalomethanes (TTHM) and haloacetic acids (HAA5): Missouri’s yearly averages per water system, as CDC’s Environmental Public Health Tracking Network publishes them, 2020 to 2023, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

81.4ppb

Highest yearly average, 2020 to 2023

2023 average: 70.2 ppb

Averaged by year, the highest was 81.4 ppb, in 2020, above EPA’s legal limit of 80 ppb. In 2023, the latest year on file, it averaged 70.2 ppb. EPA recorded violations for total trihalomethanes (TTHM) at this utility in 2020, 2024, 2025 and 2026. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 92.7 ppb, in 2015, and EPA recorded violations in 2016 and 2019.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

13.7ppb

90th percentile, 2023 to 2025

In the latest period, 9 in 10 homes sampled were at or below 13.7 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027, and this result is at or above that. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits1

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

28.4ppb

Highest yearly average, 2020 to 2023

2023 average: 14.3 ppb

Averaged by year, the highest was 28.4 ppb, in 2020, below EPA’s legal limit of 60 ppb. In 2023, the latest year on file, it averaged 14.3 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 34.4 ppb, in 2014.

What handles it

No certification claim covers this compound yet.

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

  • NSF/ANSI 53

    Claims: Trihalomethanes (TTHM) Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Lead

    Other certifiers’ wording: VOC Reduction

  • NSF/ANSI 58

    Claims: Trihalomethanes (TTHM) Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Lead

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. How whole-house systems compare.

Filters with those claims on a certifier’s listing

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Compare five-year costs

The best water filters for lead, ranked

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2026 to March 31, 202688 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2025 to Dec. 31, 202584 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2025 to Sept. 30, 202581 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2025 to June 30, 202585 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2024 to Dec. 31, 202488 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2024 to Sept. 30, 202497 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2024 to June 30, 202489.1 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2020 to Dec. 31, 202085 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2020 to Sept. 30, 202085 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2020 to June 30, 202083 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2019 to Sept. 30, 201983 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2016 to June 30, 201682 UG/LResolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 5 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Total trihalomethanes (TTHM) and haloacetic acids (HAA5) results here are Missouri’s yearly averages as CDC publishes them, from 2020 on, with EPA’s national file for 2012 to 2019. Mercer PWS’s own annual report, which it must send you every year, has the contaminants this page does not show.

  • Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.

  • What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.

  • Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; CDC’s yearly averages for Missouri cover 2020 to 2023.

Testing your own tap

Mercer PWS’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab Missouri certifies.

The 3 labs Missouri certifies closest to the area Mercer PWS serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • North Central Missouri Regional Water Commission

    Milan, MO · about 32 miles

    Certified for bacteria

    (660) 256-3807

  • Microbac Laboratories Inc.-Centerville

    Centerville, IA · about 34 miles

    Certified for bacteria

    (641) 792-8451

  • Rathbun Regional Water Association

    Centerville, IA · about 34 miles

    Certified for bacteria

    (641) 647-2416

Missouri State Public Health Laboratory: Coliform and E. coli testing for private wells and other private drinking water sources, in kits from your local public health agency. A free state courier can carry the sample to the lab overnight. The handling fee is $10, by check or money order. Private Drinking Water Bacteriological Testing, Missouri Department of Health and Senior Services.

All 64 certified labs for Missouri

Sources

PWSID MO2010515. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Nearby

All Missouri utilities

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