tapwaterdata/us-water-hardness
US Water Hardness Dataset Measured drinking-water hardness for 16,561 US cities — mg/L as calcium carbonate and grains per gallon (gpg), each value carrying its source, tier, and sample date. Canonical, continuously-updated source: https://www.tapwaterdata.com/water-hardness GitHub mirror: https://github.com/Tapwaterdata/water-hardness-dataset DOI: 10.5281/zenodo.21315903 Files water-hardness.csv — 16,561 rows, 17-column header. water-hardness.json — same 17… See the full description on the dataset page: https://huggingface.co/datasets/tapwaterdata/us-water-hardness.
US Water Hardness Dataset
Measured drinking-water hardness for 16,561 US cities — mg/L as calcium carbonate and grains per gallon (gpg), each value carrying its source, tier, and sample date.
- Canonical, continuously-updated source: https://www.tapwaterdata.com/water-hardness
- GitHub mirror: https://github.com/Tapwaterdata/water-hardness-dataset
- DOI: 10.5281/zenodo.21315903
Files
water-hardness.csv— 16,561 rows, 17-column header.water-hardness.json— same 17 fields as structured JSON + a_metablock.
Columns
slug, city, state, stateCode, lat, lng, population, hardness_mg_l, hardness_gpg, category, tier, source, sourceDate, nSamples, disputed, range_min, range_max
- category — USGS band: soft (0–60), moderatelyhard (60–120), hard (120–180), veryhard (>180 mg/L).
- tier — T1 utility-reported · T2 computed from utility Ca+Mg · T3 county ambient estimate (EPA/USGS Water Quality Portal).
Methodology
Derived from public primary sources — utility Consumer Confidence Reports, the EPA/USGS Water Quality Portal, and USGS classification bands — population-weighted per city and verified against a hand-checked golden sample. Full methodology: https://www.tapwaterdata.com/water-hardness/methodology
License
CC BY 4.0. Suggested citation: TapWaterData US Water Hardness Dataset, 2026. https://www.tapwaterdata.com/water-hardness — CC BY 4.0