The formation of the ice growth that occurs in 45° curved and straight pipes containing water flow was investigated experimentally. The experiments were carried out under various experimental conditions over the range of Reynolds numbers (based on pipe i.d.) Re=310-6760 and cooling temperature ratios of the freezing parameter. T*(=(Tf-Tw)/(T∞-Tf), Tf=0°C, Tw=cooling pipe temperature, T∞=temperature of flowing water) =1.25 - 12.9. From the visualization of ice formation in the pipes, the 45° curved pipe with flowing water was first blocked by ice formation after the curved portion of the pipe, subsequently the upstream side of the curved portion, which had already had a narrow flow passage by ice formation, was frozen off and eventually freezing of the remaining water in the curved portion resulted in a pipe rupture at around the curved portion of the pipe. The transient behavior of ice formation, according to time proceeding, was expressed in the relationship between the pressure loss coefficient f and the Reynolds number for various cooling temperature ratios T*. In addition, the critical condition of the complete ice blockage in the 45° curved and straight pipes was obtained with experimental correlation equations in terms of T* and Re.