S.C. Code Ann. § 44-55-440

In case a person subject to the provisions of this article shall have installed, prior to June 3, 1951, in his tenement or mill village an adequate sewage system with adequate water closets in compliance with the law as it then existed on the subject, such person shall be exempt from the provisions hereof, except the requirement of maintenance in compliance with the rules and regulations of the Department of Health and Environmental Control.