An apparatus for sensing an obstruction within a tube being cleaned and repetitively advancing and retracting a flexible high pressure fluid cleaning lance within the tube is disclosed. The apparatus monitors drive roller/belt position and actual hose position, compares the belt (expected travel) to hose position (travel) and generates a position difference, or mismatch. If the mismatch is above a predetermined level, the drive motor direction is reversed for a predetermined time interval, and forward operation restored after the predetermined time interval; and the sequence of repeating the reversing and restoring operations is continued until the position difference or mismatch no longer exceeds the predetermined difference threshold.