What is the Difference Between Total Alkalinity and pH?

The difference between total alkalinity and pH lies in their definitions and the factors they measure in water chemistry:

pH is a measurement of the concentration of hydrogen ions (H+) in water, indicating the acidity or basicity of the solution. It is measured on a logarithmic scale ranging from 0 to 14, with lower values indicating acidity and higher values indicating alkalinity. For example, a pH value of 7 is considered neutral, while values below 7 indicate acidic conditions, and values above 7 indicate alkaline conditions.
Total Alkalinity is a measurement of the concentration of all alkaline substances dissolved in the water, such as bicarbonate, carbonate, and hydroxide. It is primarily a reflection of bicarbonate and carbonate alkalinity and is measured in parts per million (ppm). Total alkalinity is the water's ability to resist a reduction in pH, which means that the higher the total alkalinity, the more resistant the water is to pH changes.

While both pH and total alkalinity are important in maintaining the overall balance and stability of water, they serve different purposes. pH is a direct measurement of the acidity or basicity of the solution, while total alkalinity reflects the buffering capacity of the water against changes in pH. Monitoring and controlling both pH and total alkalinity is essential for maintaining water quality and preventing potential issues, such as corrosion or scaling, in various applications, including swimming pools and water treatment systems.