City of Thompson Falls
EPA ID: MT0000341 · 1,950 people served · 1 ZIP code
Over the tracked period, City of Thompson Falls logged 4 EPA violations — each has been remedied, and the system now supplies 1,950 people in good standing.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for City of Thompson Falls Source: EPA SDWIS service area boundaries.
Service area boundary — Grade C
Service Area Demographics
The City of Thompson Falls serves a community with a median household income of $54,176 and an estimated 2,983 residents across its service area. Approximately 56% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
Environmental Justice Note: 100% of the population in this service area is classified as disadvantaged under EPA's EJScreen criteria. Communities with higher disadvantaged populations often face disproportionate environmental and health burdens, including aging water infrastructure and limited resources for remediation.
💧 Where Does Your Water Come From?
City of Thompson Falls's water is pumped from underground aquifers. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
About 3% of homes in Sanders County, Montana rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Infrastructure Risk
Detected Contaminants
How City of Thompson Falls compares to EPA limits
What This Means For You
Arsenic at 1 mg/L exceeds the EPA maximum of 0.01 mg/L.
Surface Water Treatment Rule at 2 mg/L exceeds the EPA maximum of mg/L.
Consumer Confidence Report Rule at 1 mg/L exceeds the EPA maximum of mg/L.
Comparable Water Systems
Similar-sized systems in Montana
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
City of Thompson Falls (EPA ID: MT0000341) is a community water system in Montana that serves approximately 1,950 people from groundwater sources.
This system serves ZIP code 59873 in Thompson Falls.
Average Home Safety Score: C (64/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| January 1, 2024 | Arsenic | Monitoring | Resolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Surface Water Treatment Rule | Treatment Failure | 2 | No |
| Arsenic | Inorganic | 1 | No |
| Consumer Confidence Report Rule | Reporting Failure | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 59873 | 0.001 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 1 (High Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
- 59873 — Thompson Falls
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for City of Thompson Falls (MT0000341) on EPA.gov.
Frequently Asked Questions
Is City of Thompson Falls water safe to drink?
City of Thompson Falls has only monitoring/reporting violations, which are procedural in nature. The system meets federal health-based standards.
How many people does City of Thompson Falls serve?
City of Thompson Falls serves approximately 1,950 people across 1 ZIP code in Montana.
Where does City of Thompson Falls get its water?
The primary water source is groundwater.
Water Source & Treatment
Where this water originates and how it's treated before reaching your tap.
Source: Thompson Falls City of Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility. Treatment and source data are sourced from the utility's published CCR filings.
Treatment regime
How this utility classifies its treatment process and what each reported treatment chemical does.
Treatment classification and chemical list sourced from Thompson Falls City of Consumer Confidence Report.
Treatment intensity is a ZipCheckup-derived classification based on the chemicals and processes the utility reports. Chemicals and contamination sources are taken verbatim from the utility's CCR filing. Routine federal monitoring and contaminant testing shown elsewhere on this page determine whether the water meets safety standards, not the treatment classification.
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
City of Thompson Falls (EPA ID: MT0000341) — request the latest Consumer Confidence Report or ask about specific contaminants.