Abstract: A device for repairing a main (1) can also be used to repair a leaking, corroded section of a branch pipe (2) which opens into the main. The device has a toothed rod (17) which can be extended approximately radially and rotated in the axis of the branch pipe by rotation of a pipe end cover plate (14). A hose (23), which extends from the center of the pipe end cover plate (14), is fastened to the free end of the toothed rod by means of a pipe piece (29). An air bubble (31) is placed on the pipe piece (29) and inflated by compressed air blown through the hose until it becomes lodged in the branch pipe itself. After the air bubble is detached, a cover plate is mounted on the end of the hose and a hardenable material is pumped through the hose into the cavity formed between the cover plate and the air bubble (31).