BrewWater
Glossary
Short answer
The four terms that carry most of the confusion in this subject. Hardness and total dissolved solids are routinely treated as the same measurement and are not. Alkalinity and carbonate hardness overlap but are measured from opposite sides.
- total alkalinity in water
- Total alkalinity is the capacity of water to neutralise acid without its pH falling, conventionally expressed as milligrams per litre of calcium carbonate equivalent.
- total dissolved solids (TDS) in water
- Total dissolved solids is the combined mass of all dissolved substances in water — minerals, salts and organic matter — reported in milligrams per litre.
- water hardness
- Water hardness is the traditional measure of the capacity of water to react with soap, caused by dissolved polyvalent metallic ions — predominantly calcium and magnesium — and expressed as milligrams per litre of calcium carbonate equivalent.
- carbonate hardness
- Carbonate hardness is the fraction of total hardness associated with carbonate and bicarbonate ions, which precipitates when water is heated. It is also called temporary hardness.