Head-to-head water quality
Los Angeles, CA vs Seattle, WA
Side-by-side water quality comparison: Los Angeles (Grade F) vs Seattle (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
Los Angeles
Seattle
Better
Violations subscore / 45
0.0
0.0
Tie
Lead/Copper subscore / 20
20.0
16.0
Los Angeles
Contaminant subscore / 20
10.8
14.3
Seattle
Compliance subscore / 10
8.0
8.0
Tie
Source subscore / 5
4.0
4.0
Tie
Lead & copper at the tap
Lead and Copper Rule (LCR) 90th-percentile readings — the value that 10% of sampled homes exceed.
Factor
Los Angeles
Seattle
Better
Lead 90th-percentile (latest) · EPA action level: 15 µg/L
0.0 µg/L
0.0 µg/L
Los Angeles
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
Los Angeles
Seattle
Better
PFAS analytes detected
1 of 30
0 of 30
Seattle
PFAS exceeds federal MCL
No
No
Tie
PFAS hazard index · Sum of (max/MCL) across detected analytes; > 1 indicates exceedance
—
—
—
Violation history
SDWA enforcement actions — fewer is better.
Factor
Los Angeles
Seattle
Better
Violations (last 5 years)
27
270
Los Angeles
Health-based violations (total)
94
138
Los Angeles
Unresolved violations
39
120
Los Angeles
Other contaminants tested
UCMR rounds 1–4 + UCMR 5 lithium. Maxima where data exists; "—" means not tested.
Factor
Los Angeles
Seattle
Better
Chromium-6 (max)
3.26 µg/L
0.20 µg/L
Seattle
HAA5 (avg)
6.04 µg/L
24.10 µg/L
Los Angeles
Manganese (max)
2.43 µg/L
6.50 µg/L
Los Angeles
Strontium (max)
1040.00 µg/L
38.00 µg/L
Seattle
1,4-Dioxane (max)
0.93 µg/L
—
Los Angeles
Vanadium (max)
4.18 µg/L
0.97 µg/L
Seattle
Chlorate (max)
307.00 µg/L
61.00 µg/L
Seattle
Molybdenum (max)
10.10 µg/L
—
Los Angeles
Industrial proximity
Superfund National Priorities List + Toxic Release Inventory facilities within 10 miles of the city centroid.
Factor
Los Angeles
Seattle
Better
Superfund sites within 10 mi
0
7
Los Angeles
TRI lbs to surface water within 10 mi (2023)
1,705,351
16
Seattle
System size & source
Factor
Los Angeles
Seattle
Population served
3.9M
1.2M
—
Water source
Surface water
Surface water
—
Number of water systems
16
14
—
See the full reports
Frequently asked
Which has better water — Los Angeles or Seattle?
Los Angeles, CA scores higher (42.8 vs 42.3) on WaterVerge's 100-point methodology, earning a Grade F compared to Seattle'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.