U.S. Air Force Staff Sgt. Ronald Owen, 633rd Civil Engineer Squadron water and fuel systems maintenance technician, tests the back flow preventer at the two million gallon water tank at Langley Air Force Base, Va., Nov. 6, 2015. The maintenance test ensured that no contaminates could get into the base water supply. (U.S. Air Force photo by Staff Sgt. John D. Strong II/Released)