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

A pH range of 8.0-9.0 is conducive to the deposition of calcium carbonate on the inside surface of a pipe due to the increased solubility of calcium ions and carbonate ions under alkaline conditions. When the water's pH exceeds 8.0, it indicates a more basic or alkaline environment, which can lead to a saturation of calcium carbonate in the water. If the water becomes supersaturated, calcium carbonate can precipitate out and form a thin film on surfaces, such as the inside of pipes.

Water with a pH in the lower ranges, such as 2.0-3.0, 4.0-5.0, and even 6.0-7.0, tends to be more acidic or neutral, which makes it less likely for calcium carbonate to precipitate. In acidic conditions, calcium carbonate is more soluble and remains in the aqueous phase, preventing deposition on surfaces. As the pH approaches or exceeds 8.0, the conditions favor the supersaturation of calcium carbonate, leading to potential scaling and deposition on pipes. Thus, the pH range of 8.0-9.0 is significant in understanding calcium carbonate behavior in water distribution systems.