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The objective of the study was to analyse dents in PVC-U sewer pipes observed in the initial phase of the operation called the “burn in” period. It is a part of the “bath curve” that shows the whole service life of pipes, and which also includes two further subsequent phases, namely normal operation and “wear out “ period. CCTV investigations were conducted in eleven cities. The analysis focused on quantitative data concerning size and frequency of dents observed in the walls of PVC-U sewers. Classification of dents was pro-posed, based on the dent size defined as the dent depth to the pipe diameter ratio. The rea-sons for dent occurrence were indicated. It was explained why trenchless rehabilitation of PVC-U pipes with dents cannot be performed using close-fit methods.