S.C. Code Ann. § 40-49-350

No certificate issued under the provisions of this article shall authorize the holder thereof to engage in the business of installing sanitary plumbing or to install sanitary plumbing in any city or town in the county having a population of fifteen thousand inhabitants or more as fixed by the then most recent Federal census. No person holding only a certificate granted by a board of plumbing examiners created under SECTION 40-49-290 may engage in the business of installing sanitary plumbing or install sanitary plumbing outside of the territory comprised within the municipality or the incorporated community or water, sewer or public service district whose governing board created the board which granted such certificate.