A system and method are disclosed for removing residual concrete from the interior of a ready mixed concrete truck drum using a high-pressure water jet without requiring drum entry. A nozzle housing on an elongated boom contains a rotatable nozzle driven by a motor. An encoder provides nozzle position feedback to a control system that can dynamically set and adjust the nozzle sweep limits, including independent forward and rear stop limits, and can hold the nozzle at a selected angular position. Boom translation can be referenced from a user-set zero position and displayed as travel from the reference. In some embodiments, a dual-controller arrangement includes a mounted controller and a handheld controller synchronized over a communication link with command arbitration. Safety features can include sensor-initiated rapid hydraulic power-down and a breakaway hinge configured to separate at a threshold below a boom plastic deformation threshold.