The invention relates to a device for retrograding residential and municipal drainage pipes. Specifically, when the external pipe is blocked, the countercurrent sewage is blocked by the check ball in the device, preventing the backflow from occurring, and the normal drainage is not affected. At present, well-known residential and municipal sewers do not yet have a simple and effective means of preventing the backflow of sewage. For a long time, Qingdao alone has a large number of submerged incidents of low-level households due to the blockage of drainage pipes in residential buildings, causing heavy losses to lower-level households. For example, senior floors are soaked in sewage, indoor odor is bad, contradictions exist between upper and lower households, and even Another channel through their own drainage pipes, so that the upper floor residents have to find a way to self-protection, the same municipal drainage often tidal effect of the sea water intrusion, but also an urgent need for a reliable device to prevent intrusion, and must be able to withstand greater anti To stress. The purpose of the utility model is to provide a compatible with the existing drainage pipe system, size and material corresponding to the adoption of the funnel tube and the method of counter-ball to overcome these shortcomings, to achieve a simple, practical, reliable, economical, safe Drainage pipe to achieve the purpose of anti-intrusion. The technical scheme of the utility model is as follows: Firstly, a joint with the same diameter as an existing indoor water basin, toilet, floor drain or urban sewage pipe and the like with an inlet pipe with a taper of 30 degrees and an outlet with a diameter expansion 1 times, 20mm length (or outer wire) funnel tube, and reducer pipe (or large mouth 20 mm long wire) large mouth to plug (or through the coarse screw fasteners 1/4 weeks) connected to form a closed empty Room, and then the diameter of the funnel inlet diameter of 1.2-1.5, similar to the ping pong ball, the appearance of a 1-2 mm thick oil elastic rubber (Ding Qing rubber) of the check ball placed in the empty room, The outlet is connected to a common "U" pipe of the same diameter as the original drain pipe (hose can also be used, but the water surface is higher than the empty centerline). The beneficial effect of the utility model is that the normal drainage does not affect; when the outer pipe is blocked, the anti-stop ball and the funnel form an inverse one-way passage to prevent the backflow from occurring; as the upper household continuously increases drainage, the inner part of the pipe Pressure is more and more, will cause the blockage of slippery or even disintegration of their own; even if the pressure is not high, if the blocked other drainage outlets have a backstop device, but also easy to use the earth plug and other simple gas tools can solve the pipeline Blockage problem.