A method for operating a device that conveys a fluid includes: A) detecting activation of the device; B) filling a conveying line with the fluid by operating at least one pump in a conveying direction from at least one tank to at least one injector, and detecting complete filling of the conveying line based on at least one sudden pressure increase at at least one pressure sensor; C) operating the pump and making available fluid at the injector; D) detecting deactivation of the device; and E) partially emptying the conveying line by sucking back the fluid by operation of the at least one pump in a direction counter to the conveying direction. The emptying is stopped if pressure measured at the at least one pressure sensor corresponds to an ambient pressure.