Water which does not lather readily with soap is called hard water Hardness of water is caused by the presence of dissolved salts of calcium ion, magnesium ion or iron(III) ion in water Water which lather readily with soap is called soft water. Soft water does not contain calcium ion,magnesium ion or iron(III) ion Advantages of hard water * Has pleasant taste so used in brewery industry * Hard water provides calcium, which is essential for bones, teeth, and shells formation in animals * Hard water provides Ca2+ ions which help in blood clotting in animals * Hard water provides Ca2+ ions which are used by plants to manufacture certain vital substances * Reduces heart disease Disadvantages of hard water * It wastes soap * It interferes with dyeing and tanning process. * It tends to make white clothes grey when they are laundered. Advantages of soft water * Lathers well with soap, does not form scum therefore saves soap * Suitable for dyeing and tanning * Does not form scale in boilers, kettles, radiators etc. Disadvantages of soft water * Has unpleasant taste * Lack of Ca2+ ions causes weak teeth and bones and does not promote good growth in shellfish, crabs and snails * Increase the chance of heart disease