Is Black Diamond, 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 ↓
59.8/100
waterverge.com Black Diamond, WA — Water Quality Report
Black Diamond's drinking water received a grade of C- (59.8 out of 100), indicating poor water quality. The city's 6 water systems serve approximately 3,152 residents using groundwater.
Lead levels were measured at 1.5 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 464 violations on record, including 13 health-based violations. 26 remain unresolved.
What to know about Black Diamond's water
Black Diamond ranks #193 out of 294 cities in Washington for water quality, placing it below average in the state.
Black Diamond 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, Black Diamond may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Black Diamond, WA water safe to drink?
Black Diamond's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (59.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 6 water systems serve approximately 3,152 residents using groundwater (wells).
Recent water quality updates for Black Diamond
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Black Diamond's water quality assessment. Grade: C- (59.8/100).
Federal disaster declaration (FEMA DR-3629). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
Contaminants: Nitrate.
Contaminants: Lead and Copper Rule.
Federal disaster declaration (FEMA DR-4539). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Black Diamond'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
Black Diamond's water system has 464 total violations on record, including 13 health-based violations. 26 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
King County has experienced 10 federally declared disasters since 1990. 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 White River, White River Flume, White River Above Boise Creek, Boise Creek, Newaukum Creek.
Where does Black Diamond's water come from?
Black Diamond's drinking water comes from groundwater (wells), supplied by 6 water systems serving approximately 3,152 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include White River (river), White River Flume (river), White River Above Boise Creek (river), Boise Creek (river), Newaukum Creek (river).
What Black Diamond residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Black Diamond'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.
Black Diamond'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 Black Diamond
Industrial polluters nearby
Reported releases to surface water by facilities near Black Diamond, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
FLUID MOTION LLC AUBURN, WA98002 | — | — | 9.9 mi |
SKILLS INC AUBURN, WA98002 | — | — | 9.6 mi |
PARKER HANNIFIN HELAC CYLINDER DIV ENUMCLAW, WA98022 | — | — | 7.7 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Black Diamond
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.
- QUEEN CITY FARMS9.4 mi
Source: EPA Superfund National Priorities List
Flood & disaster history
King County has experienced 10 federally declared disasters since 1990. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Black Diamond'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. | 1.5 | 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. | 2.20 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Black Diamond compares by contaminant
Explore where Black Diamond ranks among all Washington cities for specific contaminants.
Water source & infrastructure
Where Black Diamond's water comes from
Black Diamond'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 3,152 people through 6 water systems.
Water bodies near Black Diamond
Black Diamond is located near 5 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Black Diamond
| System Name | PWSID | Population | Source |
|---|---|---|---|
| BLACK DIAMOND WATER DEPT | WA5307220 | 2,420 | GW |
| WESTERN RANCHETTES INC. | WA5395123 | 250 | GW |
| SOUTH AUBURN WATER ASSOCIATION | WA5381400 | 212 | GW |
| MARIANI WATER SYSTEM INC | WA5351675 | 138 | GW |
| Creekside Apartments | WA5345164 | 100 | GW |
| SAWYERWOOD WATER SYSTEM | WA5376462 | 32 | GW |
How Black Diamond compares
Full Washington rankings →Black Diamond's score of 59.8/100 is above the average of 53/100 among major Washington cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Washington rankings →About Black Diamond, WA
Wikipedia →Black Diamond is a city in King County, Washington, United States. The population was 4,697 at the 2020 census. In 2023, with a 40.6% growth rate, Black Diamond was the fastest growing small city in King County.
Learn more about your water
Guides and resources related to Black Diamond's water quality findings.
Explore water quality across King
Frequently asked questions
Is Black Diamond, WA tap water safe to drink?
Black Diamond's water quality earned a grade of C- (59.8/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #193 out of 294 cities tested in Washington.
What contaminants are in Black Diamond's water?
Lead was measured at 1.5 ppb (90th percentile). 464 violations are on record.
How is Black Diamond'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 Black Diamond?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Black Diamond's water come from?
Black Diamond's water is sourced from Groundwater. The city has 6 water systems serving approximately 3,152 residents.
What health violations has Black Diamond's water system had?
Black Diamond has 13 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. 26 violations remain unresolved.
Is Black Diamond's groundwater at risk of contamination?
Black Diamond 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 464 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 Black Diamond's water compare to other cities?
Black Diamond ranks #193 out of 294 cities in Washington (better than 34% of state cities) and #12142 out of 15744 cities nationally (23th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.