Is Potosi, MO Tap Water Safe to Drink?
Graded C+, with 29 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
69.3/100
waterverge.com Potosi, MO — Water Quality Report
Potosi's drinking water received a grade of C+ (69.3 out of 100), indicating fair water quality. The city's 3 water systems serve approximately 3,930 residents using groundwater.
Lead levels were measured at 1.6 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 156 violations on record, including 109 health-based violations. 29 remain unresolved.
What to know about Potosi's water
Potosi ranks #410 out of 509 cities in Missouri for water quality, placing it among the lowest-rated in the state.
Potosi 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.
Water quality score
See methodology →Is Potosi, MO water safe to drink?
Potosi's drinking water has significant quality concerns based on EPA testing data. With a grade of C+ (69.3/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 3 water systems serve approximately 3,930 residents using groundwater (wells).
Recent water quality updates for Potosi
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Potosi's water quality assessment. Grade: C+ (69.3/100).
Contaminants: Consumer Confidence Rule.
Contaminants: Public Notice.
Contaminants: Revised Total Coliform Rule.
Federal disaster declaration (FEMA DR-4317). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4250). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Potosi's water supply.
Well within EPA limits.
Violation history
Potosi's water system has 156 total violations on record, including 109 health-based violations. 29 remain unresolved. 5 violations were issued in the last 5 years.
Flood & environmental risk
Washington County has experienced 6 federally declared disasters since 1993. 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 Big River At Irondale.
Where does Potosi's water come from?
Potosi's drinking water comes from groundwater (wells), supplied by 3 water systems serving approximately 3,930 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Big River At Irondale (river).
What Potosi residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Potosi'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.
Potosi'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 Potosi
Industrial polluters nearby
Reported releases to surface water by facilities near Potosi, ranked by pounds discharged annually.
Total reported releases to surface water: 1 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
BUCKMAN LABORATORIES INC. CADET, MO63630 | Bis(2-chloroethyl) ether | 1 | 5.6 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Potosi
Superfund sites nearby
Federally tracked hazardous-waste sites on the EPA National Priorities List. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
- WASHINGTON COUNTY LEAD DISTRICT POTOSI0.4 mi
- WASHINGTON COUNTY LEAD DISTRICT FURNACE CREEK6.6 mi
- WASHINGTON COUNTY LEAD DISTRICT OLD MINES10.0 mi
Source: EPA Superfund National Priorities List
Flood & disaster history
Washington County has experienced 6 federally declared disasters since 1993. 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. | 1.6 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Potosi compares by contaminant
Explore where Potosi ranks among all Missouri cities for specific contaminants.
Water source & infrastructure
Where Potosi's water comes from
Potosi'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 3,930 people through 3 water systems.
Water bodies near Potosi
Potosi is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Potosi
| System Name | PWSID | Population | Source |
|---|---|---|---|
| POTOSI PWS | MO6010659 | 2,527 | GW |
| POTOSI EAST | MO6069096 | 900 | GW |
| WASHINGTON COUNTY PWSD 1 | MO6024633 | 503 | GWP |
How Potosi compares
Full Missouri rankings →Potosi's score of 69.3/100 is above the average of 62/100 among major Missouri cities. It outscores 5 of 10 nearby cities.
Nearby cities
View Missouri rankings →About Potosi, MO
Wikipedia →Potosi is a city and the county seat of Washington County, Missouri, United States. Potosi is 72 miles (116 km) southwest of St. Louis. The population was 2,538 as of the 2020 census.
Learn more about your water
Guides and resources related to Potosi's water quality findings.
Explore water quality across Washington
Frequently asked questions
Is Potosi, MO tap water safe to drink?
Potosi's water quality earned a grade of C+ (69.3/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #410 out of 509 cities tested in Missouri.
What contaminants are in Potosi's water?
Lead was measured at 1.6 ppb (90th percentile). 156 violations are on record.
How is Potosi'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 Potosi?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Potosi's water come from?
Potosi's water is sourced from Groundwater. The city has 3 water systems serving approximately 3,930 residents.
What health violations has Potosi's water system had?
Potosi has 109 health-based violations on record. The most recent violation was recorded in July 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 29 violations remain unresolved.
Is Potosi's groundwater at risk of contamination?
Potosi 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 156 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 Potosi's water compare to other cities?
Potosi ranks #410 out of 509 cities in Missouri (better than 19% of state cities) and #10940 out of 15744 cities nationally (31th percentile). The grade of C+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.