【Daily Question】Utilities - Water Supply and Drainage - 20200124
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Which of the following statements regarding the diameter of internal building drainage risers is in accordance with the current \"Code for Design of Building Water Supply and Drainage\"? ( ) A. The water-carrying capacity of a drainage riser is greater than that of its connected horizontal branch pipes, so its diameter can be smaller than that of the branch pipes. B. The diameter of the drainage riser in the kitchens of multi-story residential buildings should not be less than 50 mm. C. A drainage riser equipped with vent pipes has a lower water-carrying capacity compared to one without vent pipes. D. For plastic drainage risers that only have roof vents, if the diameter at the bottom of the riser is not increased, its water-carrying capacity is the same as that of cast-iron drainage risers that also only have roof vents. Answer: D
D. For plastic drainage stacks equipped only with vent pipes at the top, if the diameter of the pipe at the bottom of such stacks is not increased, their water-carrying capacity is the same as that of cast-iron drainage stacks equipped only with vent pipes at the top.