Which pH range is likely to deposit a thin film of calcium carbonate on pipe surfaces?

The formation of calcium carbonate deposits in water systems is influenced by the pH of the water. In general, calcium carbonate is more soluble in acidic environments, and its solubility decreases as the pH increases. Therefore, in the context of pH ranges, a higher pH often promotes precipitation of calcium carbonate.

In the specified range of 8.0 to 9.0, water becomes increasingly alkaline, which decreases the solubility of calcium carbonate and encourages it to precipitate. This precipitation manifests as a thin film or scale on surfaces, such as pipes and other equipment.

When the pH levels are at or above 8.0, the conditions are favorable for calcium carbonate to precipitate out of the water, leading to deposition. This phenomenon is often seen in systems where water hardness is significant, and the presence of both calcium ions and bicarbonate/CO2 equilibria allows for this reaction to take place, especially in alkaline conditions.

In lower pH ranges, such as 6.5-7.0 or even slightly above, the potential for calcium carbonate to precipitate diminishes because the water remains more soluble. Higher pH ranges, specifically over 9.0, can lead to other issues such as