Is Colby, WI Tap Water Safe to Drink?
Graded A- — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
85.7/100
waterverge.com Colby, WI — Water Quality Report
Colby's drinking water received a grade of A- (85.7 out of 100), indicating good water quality. The city's 1 water system serves approximately 1,829 residents using groundwater.
Lead levels were measured at 0.9 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 2 violations on record, including 0 health-based violations. 1 remains unresolved.
What to know about Colby's water
Colby ranks #157 out of 446 cities in Wisconsin for water quality, placing it mid-range in the state.
Colby 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, Colby may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Colby, WI water safe to drink?
Colby's tap water meets most EPA standards but has areas that warrant attention. With a grade of A- (85.7/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 1 water system serves approximately 1,829 residents using groundwater (wells).
Recent water quality updates for Colby
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Colby's water quality assessment. Grade: A- (85.7/100).
Federal disaster declaration (FEMA DR-4459). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4383). Flood event — may have impacted local water infrastructure.
Contaminants: Coliform (TCR).
Key contaminant findings
Based on the most recent EPA sampling data for Colby's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Colby's water system has 2 total violations on record, including 0 health-based violations. 1 remain unresolved.
Flood & environmental risk
Clark County has experienced 6 federally declared disasters since 1973. 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 Colby's water come from?
Colby's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 1,829 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What Colby residents can do
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.
Colby'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 Colby
Industrial polluters nearby
Reported releases to surface water by facilities near Colby, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
ALL METAL STAMPING INC. ABBOTSFORD, WI54405 | — | — | 2.5 mi |
HENRY G MEIGS ABBOTSFORD, WI54405 | — | — | 2.5 mi |
COLBY METAL INC COLBY, WI54421 | — | — | 0.5 mi |
FOREMOST FARMS USA ATHENS, WI54411 | — | — | 8.2 mi |
LAND O'LAKES PURINA FEED LLC-SPENCER SPENCER, WI54479 | — | — | 7.2 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Colby
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.
- UNITY AUTO MART4.1 mi
Source: EPA Superfund National Priorities List
Flood & disaster history
Clark County has experienced 6 federally declared disasters since 1973. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Colby's water supply, we recommend the following filter types.
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. | 0.9 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 2.10 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level (90th percentile)
Latest reading: 2.100 mg/L (1993)
EPA action level: 1.3 mg/L
See how Colby compares by contaminant
Explore where Colby ranks among all Wisconsin cities for specific contaminants.
Water source & infrastructure
Where Colby's water comes from
Colby'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 1,829 people through 1 water system.
Water systems serving Colby
| System Name | PWSID | Population | Source |
|---|---|---|---|
| COLBY WATERWORKS | WI7370169 | 1,829 | GW |
How Colby compares
Full Wisconsin rankings →Colby's score of 85.7/100 is above the average of 65/100 among major Wisconsin cities. It outscores 8 of 10 nearby cities.
Nearby cities
View Wisconsin rankings →About Colby, WI
Learn more about your water
Guides and resources related to Colby's water quality findings.
Explore water quality across Marathon
Frequently asked questions
Is Colby, WI tap water safe to drink?
Colby's water quality earned a grade of A- (85.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #157 out of 446 cities tested in Wisconsin.
What contaminants are in Colby's water?
Lead was measured at 0.9 ppb (90th percentile). 2 violations are on record.
How is Colby'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 Colby?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Colby's water come from?
Colby's water is sourced from Groundwater. The city has 1 water system serving approximately 1,829 residents.
Is Colby's groundwater at risk of contamination?
Colby 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 2 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 Colby's water compare to other cities?
Colby ranks #157 out of 446 cities in Wisconsin (better than 65% of state cities) and #5163 out of 15744 cities nationally (67th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Colby's small water system affect quality?
Colby's system serves approximately 1,829 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 2 violations on record.