Quick Definition:

Acidity describes how much acid is present in swimming pool water, or how much the water behaves like an acid.

What is Acidity?

Acidity generally describes how much acid is present in a solution, such as water.  The more acid present in water or the more water behaves as an acid, the more water is considered acidic.

How acidic aqueous (water-based) solutions are measured is by pH.  The more acid present in the water, the more acidic the solution, and the lower the pH.

Measured on a scale of 0 – 14, any value less than 7.0 is considered acidic and any value greater than 7.0 is considered alkaline.

Sources: