【Daily Question】Utilities - Water Supply and Drainage - 20200229

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Which of the following statements regarding the methods for determining the diameter of vent pipes is in line with the current \"Code for Design of Building Water Supply and Drainage\"? (  )   A. Under normal circumstances, the diameter of the vent pipe should not be less than 1/3 of the diameter of the drainage pipe. B. When the length of the vent shaft is over 50 meters, its diameter should be one size smaller than that of the drainage shaft. C. The diameter of the connecting vent pipe should not be smaller than that of the vent shaft. D. Generally, the diameter of the roof vent pipe should be one size smaller than that of the drainage shaft. Answer: C. Option A does not comply with the provisions of Article 4.6.11 of the Code for Design of Building Water Supply and Drainage Systems. The diameter of the vent pipe should not be less than 1/2 of the diameter of the drainage pipe, not 1/3. Option B does not comply with the provisions of Article 4.6.12 of the Code for Design of Building Water Supply and Drainage. When the length of the vent stack is over 50 m, its diameter should be the same as that of the drain stack. Option D does not comply with the provisions of Article 4.6.15 of the 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. Option C complies with the provisions of Article 4.6.14 of the Code for Design of Building Water Supply and Drainage.