Water Supply Act Article 64

A water supply enterprise may charge users who do not have water meters installed by other methods as approved by the authority-in-charge. The water supply enterprises may also set up the minimum rates per month for those users.
中文原文 自來水法第64條
自來水事業向未裝量水器之自來水用戶收取水費,得申請主管機關核准以其他方法計算,並得規定每月最低費額。

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