Alkaline water is different from tap because it's less acidic—it has a pH over seven, meaning that it has a lower concentration of hydrogen ions, explains Alyse Levine, R.D., founder of the Eating Reset Plan.
Time for a basic chemistry lesson: "All liquids have a measure of acidity, which is determined on the pH scale. The pH measures the concentration of hydrogen ions in the liquid, which is expressed on a scale of 0-14. Anything under seven (think black coffee, orange juice, and vinegar) is acidic, seven is neutral and above seven (like baking soda) is alkaline territory," says Levine.
The “alkaline” in alkaline water refers to its pH level. The pH level is a number that measures how acidic or alkaline a substance is on a scale of 0 to 14. For example, something with a pH of 1 would be very acidic, and something with a pH of 13 would be very alkaline.
Alkaline water has a higher pH level than regular drinking water. Normal drinking water generally has a neutral pH of 7. Alkaline water typically has a pH of 8 or 9.