The pH (for "potential hydrogen") measures a substance’s level of acidity or alkalinity. On this scale, 1.0 to 6.9 is acidic, 7.0 is neutral, and 7.1 to 14.0 is alkaline (also referred to as basic).

Acidic

Sour tastes (such as that of vinegar) come from acids, whereas alkaline substances tend to taste bitter and may seem to have a slippery feel.

Alkaline

Low alkaline waters (pH 7.1–7.5) may be perceived as sweet—this doesn’t mean that the water tastes sugary but simply that it tastes neither bitter nor sour. Since pH is a logarithmic scale, the difference of 1 degree indicates a tenfold increase or decrease in acidity or alkalinity. Water with a pH of 5, for example is ten times more acidic than that with a pH of 6. I find that my palate tends to register acidity as a major component of taste at a pH of 5 or below. The following is how I describe Orientation, or the taste of water based on the pH factor, as you’ll see in my tasting notes:

Be sure not to let the pH factor have too much influence when considering the flavor of water. In the 5 to 10 range, the pH factor plays a minor role (contributing five percent of the flavor) relative to the TDS (twenty percent) and the carbonation (seventy-five percent)

pH of common substances:
Vinegar pH 3
Wine pH 2.8–3.8
Beer pH 4–5
Milk pH 6.3–6.6
Seawater pH 8.3
Bottled water pH 5–10