Hard water is not a problem when liming as the hardness will be precipitated by the lime. However, the use of complexing agents to increase the solubility of the lime are recommended.
Water hardness is caused by calcium and magnesium in the form of bicarbonates and carbonates (temporary hardness) and chlorides, sulphates etc. (permanent hardness). Water hardness can be rated by various scales, e.g. German Degrees of hardness scale where 0-10° may be considered soft. (1° German hardness = 1 part CaO/ 100,000 parts water or 10 mg/l).