Private water sources that have a pH level of less than 5.5 may corrode plumbing and appliances. The EPA mandates the pH of tap water to be a pH of at least 6.5 to prevent corrosion. Like the Richter scale for measuring earthquake intensity, the pH scale is logarithmic. A solution with a pH of 8.0 is ten times more alkaline than a solution with a pH of 7.0. A solution with a pH of 9.0 is 100 times more alkaline than a solution with a pH of 7.0.