Can the water supply and drainage washbasin and toilet in the hotel be merged?

Hotel water supply and drainage washbasin and toilet water can not be combined.

The reason is that toilet water belongs to dung water, which needs to be discharged into septic tank before it can be discharged into sewage pipe network, while washbasin water belongs to ordinary sewage and is directly discharged into municipal sewage pipe network. Therefore, the washbasin and toilet water in the hotel cannot be combined, and I hope it will be adopted.