Abstract: A method for roof drainage for reducing urban waterlogging, the method including: arranging a drainage device on a roof, the drainage device including a drainage exit and a drainage pipe including a wall; increasing the height of the drainage exit to allow the drainage exit to be between 5 and 10 cm higher than the roof; arranging a water outlet hole having a drainage capacity on the wall of the drainage pipe at a position that has the same height as the roof or is lower than the roof; disposing a siphon including an inlet and an outlet on an upper part of the drainage pipe, allowing the inlet to face the roof, and allowing the outlet to extend into the drainage pipe; and disposing a ball cock mechanism on the wall of the drainage wall to control the water outlet hole to open or close.

Abstract: A rainwater head, including: a dome, a drainage pipe, a siphon, and a ball cock mechanism. The drainage pipe includes a drainage exit and a wall including a water outlet hole. The ball cock mechanism includes a floating ball, a connecting bar, a fulcrum, and a stopper. The drainage pipe is connected to the lower part of the dome. The drainage exit is arranged on the top of the drainage pipe. The drainage exit is adapted to be between 5 and 10 cm higher than the roof. The water outlet hole is arranged on the wall of the drainage pipe at a position having the same height as the roof or is lower than the roof. The siphon is disposed on the upper part of the drainage pipe. The inlet of the siphon faces the roof; and the outlet of the siphon extends inside the drainage pipe.