Is Theresa, WI Tap Water Safe to Drink?
Graded B, with 10 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
75.8/100
waterverge.com Theresa, WI — Water Quality Report
Theresa's drinking water received a grade of B (75.8 out of 100), indicating good water quality. The city's 1 water system serves approximately 1,262 residents using groundwater.
Lead levels were measured at 0.7 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 107 violations on record, including 3 health-based violations. 10 remain unresolved.
What to know about Theresa's water
Theresa ranks #316 out of 446 cities in Wisconsin for water quality, placing it below average in the state.
Theresa 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, Theresa may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Theresa, WI water safe to drink?
Theresa's drinking water has significant quality concerns based on EPA testing data. With a grade of B (75.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 1,262 residents using groundwater (wells).
Recent water quality updates for Theresa
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Theresa's water quality assessment. Grade: B (75.8/100).
1 health-based. Contaminants: Stage 1 Disinfectants and Disinfection Byproducts Rule.
1 health-based. Contaminants: Public Notice, LEAD AND COPPER RULE REVISIONS.
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-3249). Hurricane event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-775). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Theresa's water supply.
Well within EPA limits.
Violation history
Theresa's water system has 107 total violations on record, including 3 health-based violations. 10 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
Dodge County has experienced 3 federally declared disasters since 1976. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies.
Where does Theresa's water come from?
Theresa's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 1,262 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What Theresa residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Theresa'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.
Theresa'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 Theresa
Industrial polluters nearby
Reported releases to surface water by facilities near Theresa, ranked by pounds discharged annually.
Total reported releases to surface water: 60,348 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
GRANDE CHEESE CO BROWNSVILLE BROWNSVILLE, WI53006 | Nitrate compounds (water dissociable; reportable only when in aqueous solution) | 60,348 | 8.2 mi |
MAYSTEEL LLC ALLENTON, WI53002 | — | — | 9.0 mi |
BOYD CORP ALLENTON, WI53002 | — | — | 9.1 mi |
JOHN DEERE HORICON WORKS-DT HORICON, WI53032 | — | — | 10.0 mi |
KONDEX CORP LOMIRA, WI53048 | — | — | 6.1 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Theresa
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.
- HECHIMOVICH SANITARY LANDFILL6.4 mi
Source: EPA Superfund National Priorities List
Flood & disaster history
Dodge County has experienced 3 federally declared disasters since 1976. 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. | 0.7 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Theresa compares by contaminant
Explore where Theresa ranks among all Wisconsin cities for specific contaminants.
Water source & infrastructure
Where Theresa's water comes from
Theresa'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 1,262 people through 1 water system.
Water systems serving Theresa
| System Name | PWSID | Population | Source |
|---|---|---|---|
| THERESA WATERWORKS | WI1140154 | 1,262 | GW |
How Theresa compares
Full Wisconsin rankings →Theresa's score of 75.8/100 is above the average of 65/100 among major Wisconsin cities. It outscores 6 of 10 nearby cities.
Nearby cities
View Wisconsin rankings →About Theresa, WI
Learn more about your water
Guides and resources related to Theresa's water quality findings.
Explore water quality across Dodge
Frequently asked questions
Is Theresa, WI tap water safe to drink?
Theresa's water quality earned a grade of B (75.8/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #316 out of 446 cities tested in Wisconsin.
What contaminants are in Theresa's water?
Lead was measured at 0.7 ppb (90th percentile). 107 violations are on record.
How is Theresa'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 Theresa?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Theresa's water come from?
Theresa's water is sourced from Groundwater. The city has 1 water system serving approximately 1,262 residents.
What health violations has Theresa's water system had?
Theresa has 3 health-based violations on record. The most recent violation was recorded in September 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 10 violations remain unresolved.
Is Theresa's groundwater at risk of contamination?
Theresa 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 107 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 Theresa's water compare to other cities?
Theresa ranks #316 out of 446 cities in Wisconsin (better than 29% of state cities) and #9483 out of 15744 cities nationally (40th percentile). The grade of B reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Theresa's small water system affect quality?
Theresa's system serves approximately 1,262 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 107 violations on record.