The indicator for acidity or alkalinity is known as the pH value. A pH value of 7 means a substance is neutral; water with a pH lower than 7 is considered acidic and with a pH greater than 7 ,water is considered alkaline. The normal range for pH in surface water systems is 6.5 to 8.5. The range in a Firsth2o AWG is 6.5 to 7.5 as light alkaline.