Dataset coverage
U.S. Water Hardness Dataset
Coverage details for the public lookup powering ZIP, city, state, map, and water-system pages.
Last updated March 9, 2026.
31,389
ZIP codes
27,122
Cities
48,068
Public water systems
51
States and DC
Data Quality Summary
4,846
treated-water systems
26,311
USGS-sourced systems
7,351
estimated ZIP readings
Water System Source Counts
| Source | Systems |
|---|---|
| USGS monitoring | 26,311 |
| Nearby estimate | 13,282 |
| Annual Water Quality Report | 4,539 |
| County average estimate | 3,535 |
| California treated-water report | 290 |
| State average estimate | 94 |
| Michigan utility report | 17 |
High-Signal System Examples
New York City System
NY7003493 - New York
65 PPM - Annual Water Quality Report
Los Angeles-City, Dept. Of Water & Power
CA1910067 - California
112 PPM - California treated-water report
City Of Houston
TX1010013 - Texas
135 PPM - Annual Water Quality Report
Chicago
IL0316000 - Illinois
148 PPM - Annual Water Quality Report
Mwra
MA6000000 - Massachusetts
8 PPM - Annual Water Quality Report
Mdwasa - Main System
FL4130871 - Florida
219 PPM - Annual Water Quality Report
Use the Public Lookup
The dataset is exposed through ZIP, city, state, map, and water-system pages. For bulk or partnership questions, use the contact form on the mission page.