Is Mossyrock, WA Tap Water Safe to Drink?
Graded C- — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
56/100
waterverge.com Mossyrock, WA — Water Quality Report
Mossyrock's drinking water received a grade of C- (56 out of 100), indicating poor water quality. The city's 4 water systems serve approximately 2,386 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 104 violations on record, including 14 health-based violations. 24 remain unresolved.
What to know about Mossyrock's water
Mossyrock ranks #198 out of 294 cities in Washington for water quality, placing it below average in the state.
Mossyrock 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, Mossyrock may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
The system has seen 12 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Mossyrock, WA water safe to drink?
Mossyrock's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (56/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 4 water systems serve approximately 2,386 residents using groundwater (wells).
Recent water quality updates for Mossyrock
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Mossyrock's water quality assessment. Grade: C- (56/100).
Federal disaster declaration (FEMA DR-3629). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
1 health-based. Contaminants: Lead and Copper Rule.
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-4650). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Mossyrock'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
Mossyrock's water system has 104 total violations on record, including 14 health-based violations. 24 remain unresolved. 12 violations were issued in the last 5 years.
Flood & environmental risk
Lewis County has experienced 10 federally declared disasters since 1991. 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 Tilton River Ab Bear Canyon Creek, Cowlitz River Below Mayfield Dam.
Where does Mossyrock's water come from?
Mossyrock's drinking water comes from groundwater (wells), supplied by 4 water systems serving approximately 2,386 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Tilton River Ab Bear Canyon Creek (river), Cowlitz River Below Mayfield Dam (river).
What Mossyrock residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Mossyrock'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.
Mossyrock'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
Lewis County has experienced 10 federally declared disasters since 1991. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Mossyrock'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. | 0.0 | 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. | 1.63 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Mossyrock compares by contaminant
Explore where Mossyrock ranks among all Washington cities for specific contaminants.
Water source & infrastructure
Where Mossyrock's water comes from
Mossyrock'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 2,386 people through 4 water systems.
Water bodies near Mossyrock
Mossyrock is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Mossyrock
| System Name | PWSID | Population | Source |
|---|---|---|---|
| MOSSYROCK PUBLIC UTILITY CITY OF | WA5356350 | 1,553 | GW |
| Lewis Co Water Sewer Dist #6 | WA5344240 | 740 | GW |
| Cowlitz Indian Tribal Housing | WA5325244 | 52 | GW |
| LAKEVIEW TERRACE | WA5345365 | 41 | GW |
How Mossyrock compares
Full Washington rankings →Mossyrock's score of 56/100 is on par with the average of 53/100 among major Washington cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Washington rankings →About Mossyrock, WA
Learn more about your water
Guides and resources related to Mossyrock's water quality findings.
Explore water quality across Lewis
Frequently asked questions
Is Mossyrock, WA tap water safe to drink?
Mossyrock's water quality earned a grade of C- (56/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #198 out of 294 cities tested in Washington.
What contaminants are in Mossyrock's water?
Lead was measured at 0.0 ppb (90th percentile). 104 violations are on record.
How is Mossyrock'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 Mossyrock?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mossyrock's water come from?
Mossyrock's water is sourced from Groundwater. The city has 4 water systems serving approximately 2,386 residents.
What health violations has Mossyrock's water system had?
Mossyrock has 14 health-based violations 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. 24 violations remain unresolved.
Is Mossyrock's groundwater at risk of contamination?
Mossyrock 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 104 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 Mossyrock's water compare to other cities?
Mossyrock ranks #198 out of 294 cities in Washington (better than 33% of state cities) and #12495 out of 15744 cities nationally (21th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.