Energy-saving house building drainage device

The utility model relates to the technical field of building drainage, in particular to an energy-saving house building drainage device which comprises a plurality of drainage ditches formed in a sloping roof, a water collecting tank installed on the side wall of a building, a drainage pipe installed on the side wall of the building and a collecting box. One end of the drainage ditch is communicated with the water collecting tank; wherein the drainage pipe is communicated with the water collecting tank so as to guide water on the sloping roof to the water collecting tank, one end of the watercollecting tank is closed, the other end of the water collecting tank is communicated with the upper end of the drainage pipe so as to guide rainwater in the water collecting tank into the drainage pipe, and the lower end of the drainage pipe is communicated with the collecting box. Rainwater drained from the pitched roof is collected and utilized, and the situation that rainwater dripping from the pitched roof directly i