PURPOSE: To prevent an outlet port of a horizontal branch pipeline from being blockaded by a water membrane even if discharge of drainage flowing from a drainage vertical pipeline is increased by placing a specifically shaped drain pipe joint including a specifically shaped notch.
CONSTITUTION: Drain is flowed in a vertical pipeline 2. While forming always an air core in the vertical pipeline 2 through a spiral rib 31, the drain is flowed down along a pipe wall while making the drain as swirl. A part 71 of a water membrane 7 is widened to the outside at a portion of a notch 47 by centrifugal force. The remainder 72 of the water membrane 7 having reached the lower end 46 of a cylinder 45 is widened in the shape of a trumpet. At the same time, a break 73 of the water membrane 7 is made to occur between the part 71 of the membrane 7 and the remainder 72 of the water membrane 7. Air in a horizontal pipeline 5 is connected to an air core formed always in the vertical pipeline 2 through the break 73, so that there is no pressure variation in the horizontal pipeline 5.
KAGOSHIMA EIICHI
WATANABE MITSUHIRO
