**3.1 Calcium carbonate precipitation potential (CCPP)**

The Calcium Carbonate Dissolution Potential (CCDP) or Calcium Carbonate Precipitation Potential (CCPP) is a most reliable water stability index that is often used in the context of guidelines or regulations without leading to misunderstanding. It provides a quantitative measure of the total amount of calcium carbonate that the water will either dissolve or precipitate giving an accurate guide not only to the nature of the water, but the extent to which it is under saturated with respective to calcium carbonate or over-saturated. The CCPP is an iterative function whose complexity requires the application of computer software for its calculation, but results in the most accurate representation of the water.

When CCPP is calculated, positive values represent a propensity to precipitate calcium carbonate and negative values a propensity to dissolve calcium carbonate. When CCDP is calculated the opposite relationship is formed.

Water is then classified based on the CCPP value (expressed in mg/l CaCO3) as:

