Head-to-head water quality
Chicago, IL vs San Antonio, TX
Side-by-side water quality comparison: Chicago (Grade F) vs San Antonio (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
Chicago
San Antonio
Better
Violations subscore / 45
0.0
0.0
Tie
Lead/Copper subscore / 20
9.0
16.0
San Antonio
Contaminant subscore / 20
14.2
10.1
Chicago
Compliance subscore / 10
8.0
3.0
Chicago
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
Chicago
San Antonio
Better
Lead 90th-percentile (latest) · EPA action level: 15 µg/L
0.0 µg/L
0.0 µg/L
San Antonio
Copper 90th-percentile (latest) · EPA action level: 1.3 mg/L
2.8 mg/L
1.5 mg/L
San Antonio
PFAS — "forever chemicals"
UCMR 5 testing, 2023–2025. Federal MCLs: PFOA + PFOS = 4 ng/L; HFPO-DA = 10 ng/L.
Factor
Chicago
San Antonio
Better
PFAS analytes detected
1 of 30
4 of 30
Chicago
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
Chicago
San Antonio
Better
Violations (last 5 years)
80
86
Chicago
Health-based violations (total)
68
25
San Antonio
Unresolved violations
74
212
Chicago
Other contaminants tested
UCMR rounds 1–4 + UCMR 5 lithium. Maxima where data exists; "—" means not tested.
Factor
Chicago
San Antonio
Better
Chromium-6 (max)
0.22 µg/L
1.80 µg/L
Chicago
HAA5 (avg)
11.94 µg/L
3.96 µg/L
San Antonio
Manganese (max)
—
6.40 µg/L
San Antonio
Strontium (max)
120.00 µg/L
9800.00 µg/L
Chicago
1,4-Dioxane (max)
—
0.58 µg/L
San Antonio
Vanadium (max)
0.30 µg/L
33.00 µg/L
Chicago
Chlorate (max)
—
64.00 µg/L
San Antonio
Molybdenum (max)
1.10 µg/L
9.20 µg/L
Chicago
Industrial proximity
Superfund National Priorities List + Toxic Release Inventory facilities within 10 miles of the city centroid.
Factor
Chicago
San Antonio
Better
Superfund sites within 10 mi
0
2
Chicago
TRI lbs to surface water within 10 mi (2023)
23
251
Chicago
System size & source
Factor
Chicago
San Antonio
Population served
2.8M
2.2M
—
Water source
Surface water
Purchased surface water
—
Number of water systems
21
18
—
See the full reports
Frequently asked
Which has better water — Chicago or San Antonio?
Chicago, IL scores higher (35.2 vs 33.1) on WaterVerge's 100-point methodology, earning a Grade F compared to San Antonio'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.