With or without soda? While some prefer their water quieter, others swear by it: CARBONIC ACID! CARBONIC ACID is produced when carbon dioxide combines with water. A distinction is made here between bound and free CARBONIC ACID: The former is the carbonate or hydrogen carbonate ions dissociated in water, i.e. split up; free CARBONIC ACID, in turn, is responsible for the lime-carbonic acid balance in water. If this is not balanced, the excess, free CARBONIC ACID can attack and destroy pipes (see aggressiveness). The only thing that can stop here is heating, during which carbon dioxide escapes, or calcium hydroxide, which removes the excess CARBONIC ACID.