U.S. Air Force Airman Alex McClendon, 633rd Aerospace Medicine Squadron bioenvironmental engineering technician, samples tap water in the education center at Langley Air Force Base, Va., June 12, 2015. After sampling the water, McClendon checks water to ensure it meets the drinkable standard of between 7.2 and 8 on the pH scale and less than one percent of the water is chlorinated. (U.S. Air Force photo by Airman 1st Class Devin S. Michaels/Released)