A water that has a pH (potential hydrogen) of 3.2 would be the most acidic. That is because 7.0 is the neutral phase or measurement of a substance or a solution. Anything that is below 7.0 is acidic, the lower it is the more it becomes acidic. Anything that is higher than 7.0 is basic (alkaline) opposite with the acid, the higher it gets the more it is a basic.