Airman 1st Class Jason Singleton, 22nd Civil Engineer Squadron water and fuel systems maintenance apprentice, checks the flow rate on a control valve Sept. 30, 2014, at McConnell Air Force Base, Kansas. This is a procedure that must be performed semi-annually to ensure that the correct amount of fuel is getting pushed into the fuel separator. (U.S. Air Force photo/Airman 1st Class Colby L. Hardin)