·Fugao blowdown system: exhaust valve + extension piece + discharge plug blowdown is based on the principle of gravity, negative pressure and connector. The whole pipeline system must be a closed system. The exhaust valve is used at the end of the pipeline to ensure that the pressure in the pipeline is smaller than that outside the pipeline. When the gas pressure in the pipeline is too high, the pressure can be discharged to discharge viscous liquid;

·American sewage system: the extension piece + discharge plug shall discharge sewage by gravity, and additional flushing is required to dilute the fecal sewage by twice;

·Drain plug and extension have φ200-φ250-φ315 three specifications, corresponding to different sewage discharge areas.