Study On Influencing Factors Of Drainage Capacity Of PVC-U Special Ventilation Drainage System

With the emerging of high-rise buildings and super-high-rise buildings,the internal drainage system has become an important factor affecting the health of residential environment.In order to prevent the damage of water curvature seal of sanitary appliances from causing the toxic and harmful gases in sewage pipes to diffuse directly into indoors and affect people's health,it is necessary to have a certain understanding of the drainage capacity of the internal drainage system and its influencing factors.In this paper,a 33-storey equal-proportion special ventilation and drainage system was built on a 122.9m high full-scale experimental tower,and constant-flow drainage experiment was carried out.The effects of the following factors on the drainage capacity of the special ventilation and drainage system were studied.(1)The influence of top ventilation mode on the drainage capacity of special ventilation and drainage system.The results showed that the draiange capacity of the extended ventilation is 4L/s,the positive pressure broke the seal earlier,the draiange capacity of the side wall ventilation is 3L/s,and the negative pressure broke the seal earlier.(2)The influence of H-pipe arrangement on the drainage capacity of special ventilation and drainage system.The drainage capacity of H-pipe under three different layouts of ventilation,ventilation on each floor,one-layer interval ventilation and 2-layer interval ventilation were tested respectively.The results showed that the draiange capacity of each floor ventilation and one-layer interval ventilation is 4L/s,the positive pressure broke the seal earlier,the draiange capacity of the 2-layer interval ventilation is 4.5L/s,and the negative pressure broke the seal earlier.(3)The influence of the connection mode between the lower end of the special ventilation stack and the drainage pipe on the draiange capacity of the special ventilation and drainage system.The drainage capacity of the lower end of the special ventilation stack connected with the drainage stack and the transverse main pipe were tested respectively.The test results showed that when the lower end of the special ventilation stack is connected with the drainage stack,the draiange capacity of the system is 4L/s,and the pressure broke the seal earlier;when the lower end of the special ventilation stack is connected with the horizontal main pipe at 0.36 m or 0.9m from the downstream side of the bottom of the drainage stack by inverted three link,the draiange capacity of the system is 2L/s,the positive pressure broke the seal earlier;when the lower end of the special ventilation stack is connected with the horizontal main pipe at 0.36 m or 0.9m from the downstream side of the bottom of the drainage stack by forward three link,water rushed into the lower end of the ventilation pipe,so this connection is not feasible.(4)Through the above experimental research,it is found that the main reason for restricting the drainage capacity of the special ventilation and drainage system is the excessive positive pressure at the bottom of the system,so the positive pressure relief experiment was carried out.The results showed that when two 45 degree elbows are used to connect DN100 transverse trunk pipe,the drainage capacity is 4L/s,and the positive pressure broke the seal earlier;when the diameter of horizontal main pipe is enlarged and the large curvature variable diameter elbow is used to connect the drainage stack,the draiange capacity is 3L/s,the negative pressure broke the seal earlier.Although the positive pressure at the bottom of the system is alleviated,the fluctuation value of the negative pressure of the system increases.