Is Onaga, KS Tap Water Safe to Drink?
Graded A-, with 9 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
89.2/100
waterverge.com Onaga, KS — Water Quality Report
Onaga's drinking water received a grade of A- (89.2 out of 100), indicating good water quality. The city's 2 water systems serve approximately 2,126 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 28 violations on record, including 4 health-based violations. 9 remain unresolved.
What to know about Onaga's water
Onaga ranks #20 out of 323 cities in Kansas for water quality, placing it one of the best in the state.
Onaga 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, Onaga may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Onaga, KS water safe to drink?
Onaga's drinking water has significant quality concerns based on EPA testing data. With a grade of A- (89.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 2,126 residents using groundwater (wells).
Recent water quality updates for Onaga
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Onaga's water quality assessment. Grade: A- (89.2/100).
Contaminants: Lead and Copper Rule.
Contaminants: Lead and Copper Rule.
Contaminants: Public Notice.
Federal disaster declaration (FEMA DR-3236). Hurricane event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-1000). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Onaga's water supply.
Well within EPA limits.
Violation history
Onaga's water system has 28 total violations on record, including 4 health-based violations. 9 remain unresolved.
Flood & environmental risk
Pottawatomie County has experienced 3 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. Local water sources include Vermillion C Nr Wamego.
Where does Onaga's water come from?
Onaga's drinking water comes from groundwater (wells), supplied by 2 water systems serving approximately 2,126 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Vermillion C Nr Wamego (river).
What Onaga residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Onaga'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.
Onaga'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
Flood & disaster history
Pottawatomie County has experienced 3 federally declared disasters since 1973. 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 Onaga compares by contaminant
Explore where Onaga ranks among all Kansas cities for specific contaminants.
Water source & infrastructure
Where Onaga's water comes from
Onaga'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 2,126 people through 2 water systems.
Water bodies near Onaga
Onaga is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Onaga
| System Name | PWSID | Population | Source |
|---|---|---|---|
| POTTAWATOMIE CO RWD 3 | KS2014904 | 1,455 | GW |
| ONAGA, CITY OF | KS2014905 | 671 | GW |
How Onaga compares
Full Kansas rankings →Onaga's score of 89.2/100 is above the average of 62/100 among major Kansas cities. It outscores 10 of 10 nearby cities.
Nearby cities
View Kansas rankings →About Onaga, KS
Learn more about your water
Guides and resources related to Onaga's water quality findings.
Explore water quality across Pottawatomie
Frequently asked questions
Is Onaga, KS tap water safe to drink?
Onaga's water quality earned a grade of A- (89.2/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #20 out of 323 cities tested in Kansas.
What contaminants are in Onaga's water?
Lead was measured at 0.0 ppb (90th percentile). 28 violations are on record.
How is Onaga'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 Onaga?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Onaga's water come from?
Onaga's water is sourced from Groundwater. The city has 2 water systems serving approximately 2,126 residents.
What health violations has Onaga's water system had?
Onaga has 4 health-based violations on record. The most recent violation was recorded in December 2020. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 9 violations remain unresolved.
Is Onaga's groundwater at risk of contamination?
Onaga 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 28 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 Onaga's water compare to other cities?
Onaga ranks #20 out of 323 cities in Kansas (better than 94% of state cities) and #2973 out of 15744 cities nationally (81th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.