STUDY ON THE UNDERSTANDING OF THE DRAINAGE PERFORMANCE OF THE LOOP VENT STACK SYSTEM FOR HIGH-RISE BUILDINGS AND A PREDICTION METHOD THEREOF

In Japan at present, SHASE-S206 Plumbing Code regulates the drainage performance (permissible flow rate) of loop vent systems, but the prescribed value is not supported by systematic experimentation, and the theoretical grounds for it are yet to be clarified. Therefore, the study was conducted with the aim of clarifying the following three points: identifying the variation of internal pipe pressure and air flow rate characteristics when systematically applying drainage loads to a loop vent drainage system for high-rise buildings by the testing method specified by SHASE-S218; identifying the drainage performance of the system on the basis of the test results; and correlating said drainage performance with the permissible design flow rate specified by SHASE-S206 so as to propose new design data. Finally, to provide a theoretical basis, the analysis model for drainage/vent pipelines, which was previously proposed by the author and his fellow researchers, was expanded to propose a prediction method for identifying the drainage performance of loop vent drainage systems, and the practicality of the model was discussed. Consequently, the following points were clarified.<br> (1) In the simulation tower, the loop vent pipe connecting the horizontal fixture drain branch to the vent stack was installed in different locations; on one floor, two floors or all floors, to identify variations in the distribution of internal pipe pressure, and the maximum and minimum system values, which were obtained from the distribution of internal pipe pressure corresponding to each installation location in the single stack system (the standard system), were used as indices to quantitatively measure the relaxation rate, etc., of each value.<br> (2) In relation to (1), the flow rate of air sucked from the stack vent pipe was actually measured and it was pointed out that the measured flow rate was greater than the required flow rate calculated by the constant flow method specified by SHASE-S206, when the same drainage load flow rate was applied, and the difference between the flow rates was quantitatively obtained.<br> (3) The quantitative values of drainage performance of the respective vent systems were successfully obtained by testing the systems in accordance with SHASE-S218. The results indicated that the flow rates were below the SHASE-S206 permissible flow rate for loop vent systems when the house drain had elbows spaced at 1m or 3m intervals, i.e., not straight. However, it was indicated that the SHASE-S206 permissible flow rate could be reached more or less depending on the way of drawing the vent stack from the drainage stack and the degree of expansion of the diameter of the house drain.<br> (4) The pipe network analysis model proposed in the previous report was expanded and applied to the clarification of drainage performance of the loop vent system. Subsequently, it was indicated that when the house drain had elbows, the difference between the estimated value and the actual measured value of the maximum system value (positive pressure), a drainage performance index, was significant, but said difference was small when the house drain was straight. Therefore, the pipe network analysis model was deemed applicable. The analysis model was practically effective in the pipe configuration provided for this study, but for further study, a thorough consideration should be given to the airflow resistance in parts that constitute the model and for the optimization of suction power, while accuracy needs to be improved.