Is Dayton, WA Tap Water Safe to Drink?
Graded A-, with 5 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
89.1/100
waterverge.com Dayton, WA — Water Quality Report
Dayton's drinking water received a grade of A- (89.1 out of 100), indicating good water quality. The city's 1 water system serves approximately 3,283 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 15 violations on record, including 4 health-based violations. 5 remain unresolved.
What to know about Dayton's water
Dayton ranks #53 out of 294 cities in Washington for water quality, placing it above average in the state.
Dayton 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, Dayton may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Dayton, WA water safe to drink?
Dayton's drinking water has significant quality concerns based on EPA testing data. With a grade of A- (89.1/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 3,283 residents using groundwater (wells).
Recent water quality updates for Dayton
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Dayton's water quality assessment. Grade: A- (89.1/100).
Contaminants: Nitrate.
Federal disaster declaration (FEMA DR-4539). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-4309). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Dayton's water supply.
Well within EPA limits.
Violation history
Dayton's water system has 15 total violations on record, including 4 health-based violations. 5 remain unresolved. 1 violation was issued in the last 5 years.
Flood & environmental risk
Columbia County has experienced 8 federally declared disasters since 1964. 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 Touchet River.
Where does Dayton's water come from?
Dayton's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 3,283 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Touchet River (river).
What Dayton residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Dayton'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.
Dayton'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
D1 — moderate droughtColumbia County is currently in D1 (moderate 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
Columbia County has experienced 8 federally declared disasters since 1964. 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 Dayton compares by contaminant
Explore where Dayton ranks among all Washington cities for specific contaminants.
Water source & infrastructure
Where Dayton's water comes from
Dayton'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 3,283 people through 1 water system.
Water bodies near Dayton
Dayton is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Dayton
| System Name | PWSID | Population | Source |
|---|---|---|---|
| DAYTON WATER DEPARTMENT | WA5318250 | 3,283 | GW |
How Dayton compares
Full Washington rankings →Dayton's score of 89.1/100 is above the average of 53/100 among major Washington cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Washington rankings →About Dayton, WA
Wikipedia →Dayton is a city in and the county seat of Columbia County, Washington, United States. The population was 2,448 at the 2020 census.
Learn more about your water
Guides and resources related to Dayton's water quality findings.
Explore water quality across Columbia
Frequently asked questions
Is Dayton, WA tap water safe to drink?
Dayton's water quality earned a grade of A- (89.1/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #53 out of 294 cities tested in Washington.
What contaminants are in Dayton's water?
Lead was measured at 0.0 ppb (90th percentile). 15 violations are on record.
How is Dayton'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 Dayton?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Dayton's water come from?
Dayton's water is sourced from Groundwater. The city has 1 water system serving approximately 3,283 residents.
What health violations has Dayton's water system had?
Dayton has 4 health-based violations on record. The most recent violation was recorded in January 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 5 violations remain unresolved.
Is Dayton's groundwater at risk of contamination?
Dayton 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 15 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 Dayton's water compare to other cities?
Dayton ranks #53 out of 294 cities in Washington (better than 82% of state cities) and #3019 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.
Does Dayton's small water system affect quality?
Dayton's system serves approximately 3,283 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 15 violations on record.