Abstract: The morphology and the composition of the hard incrustation stuck on the inner wall of pipeline and the water residue have been studied using methods of x-ray diffraction analysis,scanning electron microscope, chemical analysis, etc.. It was found that the incrustation had a preffered orientation and might be considered as a large crystal of CaCO₃ with a lot of defects and inclusions in it.The method of vigorous stirring the dusty water with forced water stream is often used in order to prevent the formation of the incrustation.It was found that under such conditions the pH would become greater than 11 and a lot of small crystals of CaCO₃ will be formed quic-kly due to the common ion effect, at the same time the amorphous Mg(OH)₂ is precipited, which being adhered to the surfaces of the small crystals will stop the further growth of CaCO₃ crystal. As a result, the orien-tation of the small crystals becomes impossible and a loose water residue remains,which can be taken away easily by forced running water.