Raw waters originated in artificial reservoirs or wells in granite, sandstone or basalt areas may leak water hardness (dH below 3°) and are therefore corrosive. The same goes for the constantly increasing amounts of drinking water desalted by reverse osmosis or distillation. It has very low buffering capacity and is very corrosive without further treatment. By increasing the hardness to at least 3 °dH, corrosion in the pipe networks can be avoided. In practice, the degree of hardness is set to a value of 8 °dH in order to be able to mix drinking water from several waterworks into the distribution network.