The total hardness of water will affect the amount of soap needed to produce a suds or lather.
Hard waters are as satisfactory for human consumption as soft waters.
Excessive hardness may, however, cause laundering difficulties or produce scale in hot water tanks and on cooking utensils. Hardness is generally derived from the contact of water with natural accumulations of salts in soil and geological formations, principally limestone, dolomite and gypsum. The components of total hardness may be classified in two ways. The major cause of hardness problems is carbonate hardness. Waters over that limit should not be used if less mineralized supplies are available.