Hard water, scale, and spots on glassware

Water described as ‘hard’ is high in naturally occurring dissolved minerals, specifically calcium and magnesium carbonates (chalk).

Hard water can lead to the formation of soap scum (preventing soaps from foaming), and may leave white deposits on hard surfaces or cause scaling problems inside hot water systems and kettles.

  • Hard water does not show any adverse health effects.
  • South East Queensland water is considered ‘hard’ to ‘moderately hard’.
  • Some dishwashers require that you add salt to soften water or need to be programmed to reflect the water hardness.
  • Periodic water quality data, including hardness (calculated as CaCO3), can be found here. Conversions to different units (i.e. German degrees, mmol, etc.) can be found using this data and inputting it to a conversion tool.
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Home test

Can you form lather/foam with soap?

Hard water prevents soap from foaming. If your soap does not easily foam, then your water is considered hard.

Does the water taste chalky?

Hard water is generally described as 'chalky', whereas, soft water is often described as 'slippery'.

Possible causes

Drinking water hardness is primarily due to the source of the water (i.e. dam or river) and catchment geology.