| 摘要 |
PROBLEM TO BE SOLVED: To provide a rainwater drain pipe capable of increasing the draining quantity of rainwater to enhance the draining efficiency and satisfactorily degassing the rainwater to reduce generation of vibration or noise. SOLUTION: This rainwater drain pipe comprises a whirl guide plate 7 within a vertical pipe to guide the rainwater flowing from the upper end to the lower part with whirling. The whirl guide plate 7 has a pitch change part 6 in which the pitch space is changed so that the upper inclinationα1 is large and the inclinationα2 is reduced toward the lower part, and it is provided within the vertical pipe 1 from the upper end of the vertical pipe 1 to a required position on the lower side.
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