How does the scale get into the water?

kalk-im-wasser
Warum haben wir Kalk im Wasser?
© pixabay / LoggaWiggler

Why do we even have scale in the water and where does it come from?

Water basically consists of two hydrogen atoms and one oxygen atom, thus the well-known H20. Thus, there is no lime in the original condition of water. In order to understand how the lime gets into the water, we have to look at the normal water cycle.

The largest part of the earth’s surface (namely 71%) is covered by water. This surface water evaporates, especially at the sea surface, due to the supply of solar energy. This creates humidity in the air. Since this water vapour is lighter than air, it rises to the top of the atmosphere. Because it is colder there than on earth, the water vapour cools down and condenses, becoming fine water droplets again. But it is well known that the atmosphere also contains a certain amount of carbon dioxide (CO2). Since pure water reacts very easily with carbon dioxide, H20 combines with CO2 to form H2CO3, better known as carbonic acid. The amount of carbonic acid produced depends on the amount of carbon dioxide contained in the air. If the amount of carbonic acid increases strongly, a lot of carbonic acid can form and we speak of acid rain, which conservationists have been warning us about for some time.
Water cycle
This carbonated water cools down further in the atmosphere and eventually falls back to earth as precipitation (rain, snow or hail). If this precipitation falls into any body of water, the cycle closes and the process begins again.

But if the water falls on “solid” ground, it seeps into it. If the water enriched with carbonic acid now meets calcareous rock, which essentially consists of calcium carbonate, on its way to the groundwater, the carbonic acid dissolves this lime and combines to calcium hydrogen carbonate. This happens until the liquid is saturated, i.e. the more carbonic acid is present in the water and the more calcareous the soil is, the higher the concentration of calcium hydrogen carbonate can become. It is said that the water becomes harder the more lime is absorbed by it.

Therefore we have the lime in our groundwater, which the water suppliers bring into our households.

carbon dioxide + water + calcium carbonate => calcium hydrogen carbonate
CO2 +
H2O + CaCO3 => Ca(HCO3)2