A system for locating a casing collar includes a drill pipe sub-assembly with a drill pipe segment and detection apparatus. The detection apparatus includes a bypass port disposed in a wall of the drill pipe segment; an annular sleeve which directs fluid through the bypass port and into a drill pipe segment interior portion; an actuator which opens and closes the bypass port; and two magnetized coils which generate an electromagnetic field. The actuator closes the bypass port in response to a predetermined voltage generated by the magnetized coils when they displace past a casing collar. Also included are a weight loss detection device which detects a loss of weight in the drill pipe segment, and a depth determination device which determines a depth of the casing collar, based on detected loss of weight. Also disclosed and described are a related method and drill pipe sub-assembly.