Head-to-head water quality
Denver, CO vs San Jose, CA
Side-by-side water quality comparison: Denver (Grade F) vs San Jose (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
Denver
San Jose
Better
Violations subscore / 45
0.0
0.0
Tie
Lead/Copper subscore / 20
16.0
14.0
Denver
Contaminant subscore / 20
11.6
5.0
Denver
Compliance subscore / 10
8.0
5.0
Denver
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
Denver
San Jose
Better
Lead 90th-percentile (latest) · EPA action level: 15 µg/L
0.0 µg/L
0.0 µg/L
Denver
Copper 90th-percentile (latest) · EPA action level: 1.3 mg/L
11.1 mg/L
1.6 mg/L
San Jose
PFAS — "forever chemicals"
UCMR 5 testing, 2023–2025. Federal MCLs: PFOA + PFOS = 4 ng/L; HFPO-DA = 10 ng/L.
Factor
Denver
San Jose
Better
PFAS analytes detected
1 of 30
9 of 30
Denver
PFAS exceeds federal MCL
No
Yes
Denver
PFAS hazard index · Sum of (max/MCL) across detected analytes; > 1 indicates exceedance
—
7.90
San Jose
Violation history
SDWA enforcement actions — fewer is better.
Factor
Denver
San Jose
Better
Violations (last 5 years)
485
29
San Jose
Health-based violations (total)
104
142
Denver
Unresolved violations
183
126
San Jose
Other contaminants tested
UCMR rounds 1–4 + UCMR 5 lithium. Maxima where data exists; "—" means not tested.
Factor
Denver
San Jose
Better
Chromium-6 (max)
0.25 µg/L
7.30 µg/L
Denver
HAA5 (avg)
10.26 µg/L
13.27 µg/L
Denver
Manganese (max)
120.00 µg/L
100.00 µg/L
San Jose
Strontium (max)
260.00 µg/L
1400.00 µg/L
Denver
1,4-Dioxane (max)
—
7.80 µg/L
San Jose
NDMA (max)
4.70 ng/L
7.00 ng/L
Denver
Perchlorate (max)
—
22.30 µg/L
San Jose
Vanadium (max)
0.72 µg/L
35.00 µg/L
Denver
Chlorate (max)
—
2200.00 µg/L
San Jose
Molybdenum (max)
15.00 µg/L
19.00 µg/L
Denver
Industrial proximity
Superfund National Priorities List + Toxic Release Inventory facilities within 10 miles of the city centroid.
Factor
Denver
San Jose
Better
Superfund sites within 10 mi
5
2
San Jose
TRI lbs to surface water within 10 mi (2023)
693
12
San Jose
System size & source
Factor
Denver
San Jose
Population served
1.4M
3.2M
—
Water source
Surface water
Surface water
—
Number of water systems
43
64
—
See the full reports
Frequently asked
Which has better water — Denver or San Jose?
Denver, CO scores higher (39.6 vs 28.0) on WaterVerge's 100-point methodology, earning a Grade F compared to San Jose'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.