Is Potosi, WI Tap Water Safe to Drink?
Graded C, with 21 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
61.2/100
waterverge.com Potosi, WI — Water Quality Report
Potosi's drinking water received a grade of C (61.2 out of 100), indicating fair water quality. The city's 3 water systems serve approximately 1,115 residents using groundwater.
Lead levels were measured at 3.8 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 102 violations on record, including 16 health-based violations. 21 remain unresolved.
What to know about Potosi's water
Potosi ranks #383 out of 446 cities in Wisconsin 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.
As a small community water system, Potosi may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
The system has seen 9 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Potosi, WI water safe to drink?
Potosi's drinking water has significant quality concerns based on EPA testing data. With a grade of C (61.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 3 water systems serve approximately 1,115 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 (61.2/100).
Contaminants: LEAD AND COPPER RULE REVISIONS.
Contaminants: Lead and Copper Rule.
2 health-based. Contaminants: Stage 1 Disinfectants and Disinfection Byproducts Rule.
Federal disaster declaration (FEMA DR-3249). Hurricane event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-1369). 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 102 total violations on record, including 16 health-based violations. 21 remain unresolved. 9 violations were issued in the last 5 years.
Flood & environmental risk
Grant County has experienced 5 federally declared disasters since 1969. 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 Grant River, Platte River, Middle Fk Little Maquoketa R Nr Rickardsville.
Where does Potosi's water come from?
Potosi's drinking water comes from groundwater (wells), supplied by 3 water systems serving approximately 1,115 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Grant River (river), Platte River (river), Middle Fk Little Maquoketa R Nr Rickardsville (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.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
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: 41 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
JOHN DEERE DUBUQUE WORKS DUBUQUE, IA52001 | Zinc compounds | 41 | 8.4 mi |
LOUDSPEAKER COMPONENTS LLC LANCASTER, WI53813 | — | — | 6.7 mi |
SAFE FOOD CHEMICAL INNOVATIONS-KIELER KIELER, WI53812 | — | — | 8.5 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Grant County has experienced 5 federally declared disasters since 1969. 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. | 3.8 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Potosi compares by contaminant
Explore where Potosi ranks among all Wisconsin 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 1,115 people through 3 water systems.
Water bodies near Potosi
Potosi is located near 3 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Potosi
| System Name | PWSID | Population | Source |
|---|---|---|---|
| POTOSI WATERWORKS | WI1220117 | 718 | GW |
| TENNYSON WATERWORKS | WI1220120 | 367 | GW |
| RIVER VISTA ESTATES LLC | WI1220121 | 30 | GW |
How Potosi compares
Full Wisconsin rankings →Potosi's score of 61.2/100 is on par with the average of 65/100 among major Wisconsin cities. It outscores 5 of 10 nearby cities.
Nearby cities
View Wisconsin rankings →About Potosi, WI
Learn more about your water
Guides and resources related to Potosi's water quality findings.
Explore water quality across Grant
Frequently asked questions
Is Potosi, WI tap water safe to drink?
Potosi's water quality earned a grade of C (61.2/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #383 out of 446 cities tested in Wisconsin.
What contaminants are in Potosi's water?
Lead was measured at 3.8 ppb (90th percentile). 102 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 1,115 residents.
What health violations has Potosi's water system had?
Potosi has 16 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. 21 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 102 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 #383 out of 446 cities in Wisconsin (better than 14% of state cities) and #12006 out of 15744 cities nationally (24th percentile). The grade of C reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.