Water Hardness Classifications

« Back to Glossary Index

Water hardness is determined by measuring the concentration of dissolved calcium and magnesium—typically by complexometric titration with EDTA—and expressing it as milligrams per litre of calcium carbonate (mg CaCO₃/L). Based on that concentration, water is classified as:

  • Soft: 0 – 50 mg CaCO₃/L
  • Moderately Soft: 51 – 100 mg CaCO₃/L
  • Slightly Hard: 101 – 150 mg CaCO₃/L
  • Moderately Hard: 151 – 200 mg CaCO₃/L
  • Hard: 201 – 300 mg CaCO₃/L
  • Very Hard: over 300 mg CaCO₃/L

If neither a measured nor derived hardness value is available for a supply area, it’s marked No Info.

Water hardness down to a postcode level is now available from Doorda. Contact us to arrange a demo.

« Back to Glossary Index