[Question of the Day] Utility Engineering – Water Supply and Drainage – 20200224

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Among the following statements regarding the installation of vent pipes, which one complies with the current “Code for Design of Building Water Supply and Drainage”? (   ) A. When the designed drainage flow rate borne by a vertical drain pipe for domestic wastewater exceeds the maximum drainage capacity of a vertical drain pipe equipped with only a vent pipe extending to the roof, a main vent pipe should be installed.
B. In buildings where fixture vent pipes are installed on the drainage pipes at each floor level, a main vent pipe or auxiliary vent pipe must be installed.
C. Even in drainage systems equipped with looped vent pipes and auxiliary vent pipes, a dedicated vent pipe is still required.
D. When the number of sanitary fixtures connected to a horizontal branch pipe reaches the limit specified in the codes, a combined vent pipe must be installed.
Answer: B
Option A does not comply with the provisions of Paragraph 1, Article 4.6.2 of the current “Code for Design of Building Water Supply and Drainage”. In this case, a dedicated vent stack should be provided, not the main vent stack. Option C does not comply with the explanatory provisions of Article 4.6.6 of the current Code for Design of Building Water Supply and Drainage. The main venting riser, the auxiliary venting riser, and the dedicated venting riser produce identical results; with an annular vent in place, there is no need to use a dedicated venting riser, whether it is the main venting riser or the auxiliary venting riser. D does not comply with the requirements of Article 4.6.3 of the current Code for Design of Building Water Supply and Drainage. Under this condition, a looped vent pipe should be installed instead of a combined vent pipe.   According to Paragraph 3, Article 4.6.3 of the current “Code for Design of Building Water Supply and Drainage”, when fixture vent pipes are installed, annular vent pipes shall be provided ； According to Article 4.6.5 of this specification, when ring vent pipes are installed on the drainage pipes of each floor, a main vent shaft or a secondary vent shaft that connects the ring vent pipes of various floors should be provided; therefore, it can be concluded that B is correct.