About WaterHardnessByZip.com
Free water hardness estimates for every US ZIP code, powered by USGS and EPA data.
WaterHardnessByZip.com is a free tool that shows estimated water hardness levels for any US ZIP code. We combine data from two federal sources to give you a clear picture of water hardness in your area.
Our Data Sources
USGS Water Quality Portal
The U.S. Geological Survey monitors water hardness (calcium and magnesium) at thousands of stations nationwide. We aggregate station-level measurements to county-level medians for statistical robustness.
EPA SDWIS
The EPA's Safe Drinking Water Information System (SDWIS) maps ZIP codes to public water utilities. We show your utility name and water source type so you can find your exact hardness in their annual water quality report.
Important Limitations
Our hardness estimates are based on USGS monitoring station data, which measures natural water in streams, wells, and reservoirs. This reflects your area's geological water hardness. Your actual tap water may differ because municipal water treatment can soften or blend water from different sources. For your exact tap water hardness, check your utility's Consumer Confidence Report (CCR).
Privacy & Terms
We respect your privacy and are committed to transparency. Read our Privacy Policy and Terms of Service for full details.