Is Thayer, MO Tap Water Safe to Drink?
Graded B+, with 7 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
84.5/100
waterverge.com Thayer, MO — Water Quality Report
Thayer's drinking water received a grade of B+ (84.5 out of 100), indicating good water quality. The city's 1 water system serves approximately 2,200 residents using groundwater.
Lead levels were measured at 1.0 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 16 violations on record, including 1 health-based violation. 7 remain unresolved.
What to know about Thayer's water
Thayer ranks #239 out of 509 cities in Missouri for water quality, placing it mid-range in the state.
Thayer 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, Thayer may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Thayer, MO water safe to drink?
Thayer's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (84.5/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 2,200 residents using groundwater (wells).
Recent water quality updates for Thayer
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Thayer's water quality assessment. Grade: B+ (84.5/100).
Contaminants: Consumer Confidence Rule.
Contaminants: Consumer Confidence Rule.
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-4317). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3374). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Thayer's water supply.
Well within EPA limits.
Violation history
Thayer's water system has 16 total violations on record, including 1 health-based violation. 7 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
Oregon County has experienced 3 federally declared disasters since 2005. 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 Mammoth Spring At Mammoth Spring, Spring River Near Mammoth Spring.
Where does Thayer's water come from?
Thayer's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 2,200 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Mammoth Spring At Mammoth Spring (spring), Spring River Near Mammoth Spring (river).
What Thayer residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Thayer'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.
Thayer'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
Drought conditions
D3 — extreme droughtOregon County is currently in D3 (extreme drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
Oregon County has experienced 3 federally declared disasters since 2005. 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. | 1.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Thayer compares by contaminant
Explore where Thayer ranks among all Missouri cities for specific contaminants.
Water source & infrastructure
Where Thayer's water comes from
Thayer'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 2,200 people through 1 water system.
Water bodies near Thayer
Thayer is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Thayer
| System Name | PWSID | Population | Source |
|---|---|---|---|
| THAYER PWS | MO4010788 | 2,200 | GW |
How Thayer compares
Full Missouri rankings →Thayer's score of 84.5/100 is above the average of 62/100 among major Missouri cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Missouri rankings →About Thayer, MO
Learn more about your water
Guides and resources related to Thayer's water quality findings.
Explore water quality across Oregon
Frequently asked questions
Is Thayer, MO tap water safe to drink?
Thayer's water quality earned a grade of B+ (84.5/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #239 out of 509 cities tested in Missouri.
What contaminants are in Thayer's water?
Lead was measured at 1.0 ppb (90th percentile). 16 violations are on record.
How is Thayer'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 Thayer?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Thayer's water come from?
Thayer's water is sourced from Groundwater. The city has 1 water system serving approximately 2,200 residents.
What health violations has Thayer's water system had?
Thayer has 1 health-based violation 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. 7 violations remain unresolved.
Is Thayer's groundwater at risk of contamination?
Thayer 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 16 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 Thayer's water compare to other cities?
Thayer ranks #239 out of 509 cities in Missouri (better than 53% of state cities) and #5862 out of 15744 cities nationally (63th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Thayer's small water system affect quality?
Thayer's system serves approximately 2,200 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 16 violations on record.