A device of a water draining system for caverns is described, comprising one or more sections of tunnel covering or tunnel canvas which is arranged in the cavern at a certain distance from the walls and ceiling of the cavern, and a draining pipe system for leading away water. The device is characterized by one solid extended ceiling draining pipe, where the one longitudinal lower edge side of a first tunnel covering is arranged to the one internal side edge of the concave part of the ceiling draining pipe, while the one longitudinal lower side edge of a second tunnel covering is arranged to the other internal side edge of the concave part of the ceiling draining pipe, that the other longitudinal side edges respectively of the tunnel coverings are arranged to the ceiling or wall section of the cavern so that the canvas surfaces form a suitably inclined plane down towards the draining pipe, and that the ceiling draining pipe is secured to the ceiling section of the cavern via a number of rock bolts which are connected to and secure the ceiling draining pipe.