A fluid pumping system may comprise a pump and a fluid line state detector having, a receptacle, at sensor, and an illuminator. The system may further comprise a fluid transfer set including an output line for mating into the receptacle. The system may further comprise a controller in data communication with the fluid line state detector configured to power the illuminator and monitor an output signal of the sensor when the outlet line is in the receptacle to determine a dry tube light intensity value. The controller may be further configured to govern operation of the pump to prime the output line with fluid. The controller may be further configured to power the illuminator, monitor the output signal, and halt operation of the pump when the output signal indicates the light intensity value has dropped below a primed line threshold which is dependent upon the dry tube intensity value.
