The hardness depends mostly on the origin of the water. Those surface waters which are formed by rainwater, are very soft. The deep sources' waters often contain a high quantity of calcium.
The hardness of the water doesn't causes any diseases, but it determines the water's employability.
For the coffee-makers, washmachines, flat-irons or other setups which use warm water systems is better to use soft water, because the deposited scale from the hard water can disturb their function. That's the reason why the producers suggest the frequently cleaning up or using of those contributions which can make the water softer.
That water hardness which is suitable eg. for the fishes, can't be used for the plants' irrigation. So we have to inquire about the water's hardness before using.
