Under the subway, each station has an independent drainage system, and there is also a drainage system in the subway pipeline (tunnel).

These sewage are stored separately. Toilets are toilets, and ordinary sewage is ordinary sewage.

Then use the pool near the platform for centralized storage. The pool is only used as a buffer, and a screw pump pumps all the sewage up to the urban sewage pipeline.

In the drainage system similar to flood dike, when the external water level is higher than the internal water level, it is difficult to realize natural drainage by gravity, and then the water and other pollutants are pumped out together with the same screw pump and sent out around the dike.