Is Thompson Falls, MT Tap Water Safe to Drink?
Graded B+, with 19 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
80.6/100
waterverge.com Thompson Falls, MT — Water Quality Report
Thompson Falls's drinking water received a grade of B+ (80.6 out of 100), indicating good water quality. The city's 4 water systems serve approximately 2,345 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 108 violations on record, including 27 health-based violations. 19 remain unresolved.
What to know about Thompson Falls's water
Thompson Falls ranks #35 out of 115 cities in Montana for water quality, placing it mid-range in the state.
Thompson Falls relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Thompson Falls may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
The system has seen 6 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Thompson Falls, MT water safe to drink?
Thompson Falls's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (80.6/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 4 water systems serve approximately 2,345 residents using groundwater (wells).
Recent water quality updates for Thompson Falls
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Thompson Falls's water quality assessment. Grade: B+ (80.6/100).
Federal disaster declaration (FEMA DR-3630). Flood event — may have impacted local water infrastructure.
Contaminants: Revised Total Coliform Rule.
Contaminants: Nitrate-Nitrite.
Contaminants: Revised Total Coliform Rule.
Federal disaster declaration (FEMA DR-4172). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Thompson Falls's water supply.
Well within EPA limits.
Violation history
Thompson Falls's water system has 108 total violations on record, including 27 health-based violations. 19 remain unresolved. 6 violations were issued in the last 5 years.
Flood & environmental risk
Sanders County has experienced 5 federally declared disasters since 1974. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Thompson River Near Thompson Falls, Prospect Creek At Thompson Falls.
Where does Thompson Falls's water come from?
Thompson Falls's drinking water comes from groundwater (wells), supplied by 4 water systems serving approximately 2,345 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Thompson River Near Thompson Falls (river), Prospect Creek At Thompson Falls (river).
What Thompson Falls residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Thompson Falls's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Thompson Falls's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Thompson Falls
Industrial polluters nearby
Reported releases to surface water by facilities near Thompson Falls, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
THOMPSON RIVER LUMBER THOMPSON FALLS, MT59873 | — | — | 3.4 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Sanders County has experienced 5 federally declared disasters since 1974. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Thompson Falls compares by contaminant
Explore where Thompson Falls ranks among all Montana cities for specific contaminants.
Water source & infrastructure
Where Thompson Falls's water comes from
Thompson Falls's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 2,345 people through 4 water systems.
Water bodies near Thompson Falls
Thompson Falls is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Thompson Falls
| System Name | PWSID | Population | Source |
|---|---|---|---|
| THOMPSON FALLS CITY OF | MT0000341 | 1,950 | GW |
| SALISH SHORES TRADE WINDS COMM VILLAGE | MT0003911 | 215 | GW |
| WOODSIDE PARK COUNTY WATER AND SEWER DIS | MT0002986 | 115 | GW |
| NORTH SHORE ESTATES HOA | MT0003556 | 65 | GW |
How Thompson Falls compares
Full Montana rankings →Thompson Falls's score of 80.6/100 is above the average of 45/100 among major Montana cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Montana rankings →About Thompson Falls, MT
Learn more about your water
Guides and resources related to Thompson Falls's water quality findings.
Explore water quality across Sanders
Frequently asked questions
Is Thompson Falls, MT tap water safe to drink?
Thompson Falls's water quality earned a grade of B+ (80.6/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #35 out of 115 cities tested in Montana.
What contaminants are in Thompson Falls's water?
Lead was measured at 0.0 ppb (90th percentile). 108 violations are on record.
How is Thompson Falls's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Thompson Falls?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Thompson Falls's water come from?
Thompson Falls's water is sourced from Groundwater. The city has 4 water systems serving approximately 2,345 residents.
What health violations has Thompson Falls's water system had?
Thompson Falls has 27 health-based violations on record. The most recent violation was recorded in December 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 19 violations remain unresolved.
Is Thompson Falls's groundwater at risk of contamination?
Thompson Falls uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 108 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Thompson Falls's water compare to other cities?
Thompson Falls ranks #35 out of 115 cities in Montana (better than 70% of state cities) and #7784 out of 15744 cities nationally (51th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.