Enforcement Rules of Sewerage Act Article 18

The sewer facility for new structures that are not for public use and under five floors may be designed by the same architect of such structures.
中文原文 下水道法施行細則第18條
五層以下非供公眾使用之新建建築物,其下水道設備得由該建築物之建築師併同設計之。

English translation for reference only; the Chinese text prevails. Not legal advice.