The acidity and alkalinity of water is measured by a factor called pH. Values for pH fall on a scale ranging from 0 to 14. The normal range for water is 6.5 to 8.5. Water that has a pH of 7 is neutral; water that is acidic has a pH lower than 7 and water that is alkaline has a pH greater than 7.
Acidic water can be corrosive and may deteriorate plumbing and leach toxic metals such as lead and copper from pipes. The leaching of copper will cause a blue/green stain on fixtures. Pitted or perforated pipes and the presence of iron and other metals in tap water are also symptoms of acidity.
Alkaline water has a bitter taste, may feel slippery to the touch, cause dry skin, and contains dissolved minerals that can encrust pipes and appliances. Very alkaline water also decreases the effectiveness of water chlorination so that high levels of chlorine need to be used.