【Daily Question】Utilities - Water Supply and Drainage - 20200219

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The school canteen has two floors; the wastewater from the second-floor canteen is discharged outdoors through vertical pipes, with vent pipes installed at the top of these vertical pipes. If the design secondary flow rate for drainage in the second-floor cafeteria is 2.4 L/s and cast iron pipes are used for the drainage pipes, then the diameter of the vertical pipes should be (   ) mm. See the table below: A50          B75        C110         D125. Answer: C. According to Table 3-2, when the designed second flow rate is 24 L/s, DN75 mm meets the requirements. However, according to Article 4.4.15, Paragraph 2 of the Code for Design of Building Water Supply and Drainage, when wastewater from public cafeteria kitchens is discharged through pipes, the pipe diameter should be one size larger than the calculated value; therefore, C is the correct answer