Abstract: A method of removing undesired coatings from the interior surface of tubes includes inserting a fluid-dynamically unstable impact head into the tube, providing or maintaining fluid flow through the tube and altering the length of a tether attached to the impact head to move the impact head along the tube. As a result of the fluid flow, the impact head moves chaotically within the tube, impacting the interior surface of the tube and removing undesired coatings therefrom. An apparatus for accomplishing the method preferably includes an impact head, a flexible retaining line and a carriage moveable within the tube, the carriage aiding in the centering of the retaining line.