Double-wall ventilation and drainage pipe

The utility model provides a double-wall ventilation and drainage pipe aiming at the problem that in present building ventilation and drainage pipes, frequently-used stack vents and H-shaped special vent pipes cannot meet the requirements of great ventilating drainage capacity and space saving at the same time. The double-wall ventilation and drainage pipe is formed by sleeving of a large drainage pipe and a small drainage pipe, wherein the small pipe as an inner pipe is taken as a drainage pipe, and the large pipe as an outer pipe is taken as a ventilation pipe; the critical connection part is formed by clamping and adhering the inner pipe provided with a diversion strip and a circular hole and the outer pipe provided with a partition wall and an inclined wall for water retaining through combination; an obvious wall-attached flow is formed, the water flows through the inner pipe to form an air pressure, and the air pressure is exhausted to the outer pipe for ventilation through the circular hole in the inner