【Daily Question】Utilities - Water Supply and Drainage - 20200225

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Among the following examples, the diameter of the vent pipe specified meets the requirements of the current \"Code for Design of Building Water Supply and Drainage\" (   ).   A. A dedicated venting riser with a length of 40 m, connected simultaneously to 1 domestic sewage pipe of DN100 mm and 1 domestic wastewater pipe of DN100 mm, has a diameter of DN75 mm. B. The drainage riser in a certain building is DN100 mm; given that the average temperature in the coldest month in this area is –15°C, the diameter of the vent pipe extending above the roof is DN125 mm. C. A main venting riser connected to 1 domestic drainage pipe of DN125 mm and with a length of 60 m has a diameter of DN100 mm. D. The diameter of the circular vent pipe connected to a drainage branch pipe with a diameter of DN100 mm is DN150 mm. Answer: B. Options A, C, and D do not comply with the provisions of Articles 4.6.13, 4.6.12, and Table 4.6.11 of the current “Code for Design of Building Water Supply and Drainage”. In option A, the diameter of the dedicated venting riser should be DN100 mm ； In option C, the diameter of the main ventilation riser should be DN125mm ； In option D, the diameter of the circular vent pipe should be DN50mrn.   Option B complies with the provisions of Article 4.6.15 of the current Code for Design of Building Water Supply and Drainage. Generally, the diameter of the vent pipe should be the same as that of the drainage riser. However, in areas where the average temperature during the coldest month is below -13°C, to prevent frost formation at the pipe outlet from affecting ventilation, the diameter should be increased by one size level at a height of 0.3 m below the indoor flat roof or ceiling; therefore, B is the correct answer.