Our Mission
Accurate, free water hardness data for every household in the United States.
Why WaterHardness.org Exists
Hard water affects more than 85% of American homes, yet finding reliable hardness data for your specific location has always been surprisingly difficult. Utility Consumer Confidence Reports are published annually but they're scattered across thousands of individual water systems, often buried in PDFs, and rarely standardized.
We built WaterHardness.org to solve that. Our goal is to give every US household a fast, free way to look up their water hardness—no sign-ups, no paywalls, no sales pitches. Whether you're deciding if you need a water softener, diagnosing hard water symptoms, or just curious, this site is for you.
How We Calculate Water Hardness
We combine multiple federal and state data sources to estimate water hardness by water system, zip code, city, and state. The current dataset was last rebuilt on March 9, 2026.
1. Match systems to places
We start with active community water systems and the cities, counties, and zip codes they report serving.
2. Assign hardness readings
We attach treated-water lab results where available, then use CCR values, USGS observations, and nearby estimates when direct tap-water data is not available.
3. Aggregate locally
Zip, city, and state values are weighted toward the systems serving the most people, so larger utilities have proportionate influence on the displayed average.
Source Priority
- State Compliance Labs — Treated water lab results from state agencies (California EDT, Michigan DEQ) that reflect what actually comes out of the tap.
- Consumer Confidence Reports — Annual water quality reports published by utilities. We hand-verify CCR data for hundreds of cities with 50,000+ residents.
- EPA SDWIS — The Safe Drinking Water Information System catalogs ~48,000 active community water systems, including the areas they serve.
- USGS Water Quality Portal — Millions of water quality measurements from wells, streams, and monitoring stations across every state.
We classify hardness using the standard USGS scale in parts per million as calcium carbonate: soft below 60 PPM, slightly hard from 60-119 PPM, moderately hard from 120-179 PPM, hard from 180-249 PPM, and very hard at 250 PPM or higher. We also show grains per gallon using the standard conversion of 17.1 PPM per GPG.
When a page says a value is an estimate, that means the reading may come from nearby source-water monitoring or a broader county or state average rather than a direct treated tap-water result. Seasonal changes, utility blending, treatment changes, and household plumbing can all change your actual tap reading.
Community Submissions
We also accept water hardness readings from people who have tested their own water or found local utility reports. These submissions help us catch local variation, identify outdated utility data, and prioritize areas that need better verification.
Community readings are treated as supporting evidence. We review the test method, location, water source, and any attached documentation before using a submission. Lab reports and utility CCRs carry more weight than home test strips, and community data is labeled separately from official state, EPA, and USGS sources.
Help Us Improve
Have your utility's CCR or local water test results? Notice an error? We rely on community contributions to keep our data accurate. Send us your data and we'll verify and incorporate it.
How We Keep This Free
WaterHardness.org is free to use and always will be. We earn a small commission when you purchase water treatment products through our recommendation links. Every product we recommend is independently researched - we only suggest products we believe in, and our recommendations are never influenced by commission rates.
This revenue covers our hosting, data processing, and ongoing data verification work. We believe transparency about monetization builds trust, and trust is what makes this resource useful.
Disclaimer
Water hardness values on this site are estimates based on publicly available data from the EPA, USGS, state agencies, and utility reports. Actual tap water hardness may differ due to seasonal variation, treatment changes, or local distribution factors. For precise results, test your water directly with a certified lab or home test kit. This site is for informational purposes only and does not constitute professional advice.