Head-to-head water quality
Seattle, WA vs Tucson, AZ
Side-by-side water quality comparison: Seattle (Grade F) vs Tucson (Grade F). Lead, PFAS, violations, and source-water contamination
Score breakdown
Each factor is shown as raw points (out of the maximum). Higher = better.
Factor
Seattle
Tucson
Better
Violations subscore / 45
0.0
0.0
Tie
Lead/Copper subscore / 20
16.0
20.0
Tucson
Contaminant subscore / 20
14.3
5.1
Seattle
Compliance subscore / 10
8.0
8.0
Tie
Source subscore / 5
4.0
5.0
Tucson
Lead & copper at the tap
Lead and Copper Rule (LCR) 90th-percentile readings — the value that 10% of sampled homes exceed.
Factor
Seattle
Tucson
Better
Lead 90th-percentile (latest) · EPA action level: 15 µg/L
0.0 µg/L
0.0 µg/L
Tucson
Copper 90th-percentile (latest) · EPA action level: 1.3 mg/L
610.0 mg/L
—
Seattle
PFAS — "forever chemicals"
UCMR 5 testing, 2023–2025. Federal MCLs: PFOA + PFOS = 4 ng/L; HFPO-DA = 10 ng/L.
Factor
Seattle
Tucson
Better
PFAS analytes detected
0 of 30
8 of 30
Seattle
PFAS exceeds federal MCL
No
Yes
Seattle
PFAS hazard index · Sum of (max/MCL) across detected analytes; > 1 indicates exceedance
—
2.75
Tucson
Violation history
SDWA enforcement actions — fewer is better.
Factor
Seattle
Tucson
Better
Violations (last 5 years)
270
469
Seattle
Health-based violations (total)
138
150
Seattle
Unresolved violations
120
1,177
Seattle
Other contaminants tested
UCMR rounds 1–4 + UCMR 5 lithium. Maxima where data exists; "—" means not tested.
Factor
Seattle
Tucson
Better
Chromium-6 (max)
0.20 µg/L
9.40 µg/L
Seattle
HAA5 (avg)
24.10 µg/L
1.42 µg/L
Tucson
Manganese (max)
6.50 µg/L
120.00 µg/L
Seattle
Strontium (max)
38.00 µg/L
1700.00 µg/L
Seattle
1,4-Dioxane (max)
—
6.70 µg/L
Tucson
Perchlorate (max)
—
11.90 µg/L
Tucson
Vanadium (max)
0.97 µg/L
11.00 µg/L
Seattle
Chlorate (max)
61.00 µg/L
1100.00 µg/L
Seattle
Molybdenum (max)
—
15.00 µg/L
Tucson
Industrial proximity
Superfund National Priorities List + Toxic Release Inventory facilities within 10 miles of the city centroid.
Factor
Seattle
Tucson
Better
Superfund sites within 10 mi
7
1
Tucson
TRI lbs to surface water within 10 mi (2023)
16
0
Tucson
System size & source
Factor
Seattle
Tucson
Population served
1.2M
894K
—
Water source
Surface water
Groundwater
—
Number of water systems
14
82
—
See the full reports
Frequently asked
Which has better water — Seattle or Tucson?
Seattle, WA scores higher (42.3 vs 38.1) on WaterVerge's 100-point methodology, earning a Grade F compared to Tucson's Grade F. The score combines violation history, lead and copper levels, contaminant testing, monitoring compliance, and source-water type.
How is the WaterVerge water quality score calculated?
The grade combines five subscores: violation history (45 pts, weighted by recency and health-based severity), lead/copper 90th-percentile vs EPA action levels (20 pts), contaminant testing including PFAS, chromium-6, HAA5, NDMA, perchlorate, and Superfund/TRI proximity (20 pts), monitoring compliance (10 pts), and water-source-type risk (5 pts). Full methodology at /about/methodology.
Where does this water quality data come from?
From the EPA's public records: the SDWIS bulk download (violations + system info), UCMR rounds 1–5 (unregulated contaminant testing including PFAS, chromium-6, HAA5, NDMA, perchlorate, vanadium, lithium), the EPA Toxic Release Inventory (industrial polluters), the Superfund National Priorities List, the USGS Powell Domestic-Well Database (private-well chemistry), and the CDC Community Water Fluoridation system. Data is refreshed quarterly.