About Water Hardness Atlas
Water Hardness Atlas publishes the hardness of tap water for cities and towns, one page per place, with the official source, its date and what the number means at home.
Every figure comes from a water supplier, a health authority or a national open-data file. We never take numbers from filter sellers, blogs or AI answers. When several supply zones serve a place, we show the median and the range.
Figures from large open datasets are checked by scripts (units, plausible range, age, conflicts with other sources); a sample of every source and every flagged row is reviewed by hand. Places without an official figure have no page.
The site is independent. Some pages link to water softeners and filters as affiliate links; we earn a commission, which never changes the figures or the advice.
Found an outdated figure or a better source? Write to [email protected].