PlainWater
Contaminants →
EPA SDWIS ~155K water systems EPA + UCMR5

TTHM

EPA SDWIS quarterly extract data for this analyte. Detection counts and health-based violation counts reflect the most recent federal release.

PlainWater home → About this data

EPA contaminant code: 2950

Total Violations
327,560
Systems Affected
19,132
Health-Based %
63.4%
Most Affected State
-

What this means

TTHM appears in EPA SDWIS with 327,560 recorded violations across 19,132 public water systems. Of those, 63.4% are classified as health-based, meaning the reading exceeded a federally enforceable Maximum Contaminant Level or a treatment-technique requirement rather than a monitoring or reporting lapse. Health-based violations are the subset that trigger formal corrective action and public notification, so the share is a useful signal of real-world exposure risk rather than paperwork drift. State-level concentration data is not consistently reported for this contaminant, so regional interpretation should lean on the system table below rather than state aggregates. Utilities listed below are ranked by cumulative violation count, so a higher rank reflects persistence in the record rather than a single spike; readers comparing systems should consider population served alongside violation count to gauge how many households were actually exposed.

Violation Type Split

TTHM violations broken down by EPA classification.

Health-based (63.4%) Monitoring/Reporting (36.6%)

Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement; monitoring/reporting violations are procedural.

Most Affected Water Systems

System State Violations Population
Waurika Public Works Authority OK 726 2,100
Fairview Union Water System LA 714 2,346
Cleveland Municipal Authority OK 706 3,262
Town of Ferriday Water System LA 665 4,193
Barnsdall OK 628 1,243
Pushmataha Co. RWD #3 OK 612 4,825
Ryan Utilities Authority OK 558 800
Comanche Public Works Authority OK 553 1,649
Litroe Water System LA 533 369
Linville-Haile Water System LA 529 1,635
Hudson Gaars Mill Water System LA 528 660
Okmulgee OK 520 13,495
Maysville OK 498 1,212
Village of Calvin Water System LA 491 591
Red Hill Waterworks Inc. LA 489 1,914
Osage Co RWD #20 (Hulah) OK 489 350
Jones McGinty Water System LA 485 696
Muskogee Co. RWD #3 OK 485 1,300
Davenport Utility Auth OK 484 881
Pleasant Hills-Crossroads Water Systems LA 477 840
McIntosh Co. RWD #8 (Texanna) OK 477 3,574
Fairfax OK 476 1,555
Otoe-Missouria Tribe OK 473 250
Tri-Water System LA 466 1,302
Duncan Public Utilities Authority OK 457 23,000
Eufaula PWA OK 456 2,766
Grandfield OK 429 1,110
Pittsburg OK 428 280
Rra Preston Shores Water System TX 427 2,277
Union Springs Water System LA 424 1,260

Drinking Water Guides

Understanding Water Quality Data

What EPA SDWIS tracks, how violations are classified, and what MCLs mean.
PFAS in Drinking Water

What forever chemicals are, EPA testing results, and 2024 standards.
Is My Water Safe?

How to assess your local water quality and when to take precautions.

Frequently Asked Questions

What is TTHM in drinking water? ▼
TTHM is a contaminant tracked by the EPA under the Safe Drinking Water Act. It has caused 327,560 violations across 19,132 public water systems nationwide. 63.4% of these violations are health-based, meaning the contaminant exceeded Maximum Contaminant Levels (MCLs) or treatment technique requirements.
How many water systems have TTHM violations? ▼
19,132 public water systems across the United States have at least one TTHM violation recorded in the EPA SDWIS database.
Are TTHM violations dangerous? ▼
63.4% of TTHM violations are health-based, meaning the contaminant level exceeded safe limits set by the EPA. Health-based violations require corrective action by the water system. Not all violations indicate immediate health risk, but they signal that water quality standards were not met.
Which state has the most TTHM violations? ▼
State-level breakdown data is not available for this contaminant.
Where does this contaminant data come from? ▼
All violation data comes from the EPA Safe Drinking Water Information System (SDWIS), which tracks compliance for all public water systems regulated under the Safe Drinking Water Act. SDWIS records violations including Maximum Contaminant Level (MCL) exceedances, treatment technique failures, and monitoring/reporting issues.

Data Sources

Contaminant violation data from the EPA Safe Drinking Water Information System (SDWIS). Violations are categorized as health-based (Maximum Contaminant Level exceedances, treatment technique failures) or monitoring/reporting violations.

Related

Browse all → | Rankings →
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Disclaimer: This information is provided for informational purposes only and does not constitute professional advice. Data is sourced from the EPA Safe Drinking Water Information System (SDWIS). Consult a qualified professional before making decisions based on this data.

Read our methodology - how this data is sourced, computed, and verified.

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.