The evolution of hollow-core defects present in vapor phase grown SiC bulk crystals during subsequent liquid phase epitaxial treatment has been investigated in a wide range of supersaturation conditions. Hollow macrodefects were found to decompose into a number of micropipes (MP) already at supersaturations close to zero. The elimination of pure screw-dislocation based MP requires a higher supersaturation. Micropipes were observed to dissociate into individually acting non-hollow core dislocations. After decomposition the activity of growth center based on a MP is usually reduced and a new center may dominate the growing surface. A model for the mechanism of MP transformation is proposed which is based on BCF theory and Chernovs theory of morphological stability.