The invention relates to a device for the internal treatment of pipes, in particular for coolant tubes of steam condensers and heat exchangers, comprising a supply unit (V) for feeding and conveying treatment media, an application unit (A) to apply the treatment media fed in by the supply unit, as well as a control unit to monitor and control the supplied treatment media and the application of treatment media to the inner wall of the pipes, wherein the application unit (A) is provided with a guiding hose (21) through which an application hose (18) extends designed so as to be inserted into the pipe to be treated, said application hose (18) terminating in a nozzle, wherein the application hose (18) can be wound up in a single layer on a driven reel (17) and secured on the reel (17) by means of tensioning belts, the application hose (18) is capable of moving forward and back via guide rollers (27) arranged on a traversing carriage (55), the guide rollers (27) are powered by a drive operating synchronously with the drive (19) of the reel (17), and the traversing carriage (55) moves parallelly to the reel axis relative to the extended position of the application hose (18).