Water softening pellets. Thin section through water pellets that have been used to soften water. Water softening is the process of removing dissolved calcium ions and other mineral ions. This avoids problems with limescale formation in domestic appliances and pipes, and soap scum in water that is used for washing. The pellets are the nucleus around which calcium carbonate and other minerals form in a pellet reactor. Each of these pellets was originally a small grain of sand (silica, coloured areas) about 3-5 milimetres across. The brown layers around each grain are the minerals that have deposited on the grains.