S.C. Code § 6-21-40
The word "system" as used in this chapter shall include all of the projects and undertakings referred to in Section 6-21-50. The water and sewer systems of any municipality shall constitute one system and any two or more projects or undertakings described in Section 6-21-50 which are in any way related, as in the case of a waterworks system and a sewer system, may be deemed a single system or project for the purposes of this chapter if the governing body of the municipality establishing it shall so determine either in the ordinance authorizing the issuance of bonds pursuant to this chapter or in any other ordinance passed prior to the issuance of the bonds. Any city owning and operating a municipal airport may combine such airport with any harbor improvement plan, including one providing docking and other facilities common to marinas or yacht basins, into a single system for all of the purposes of this chapter.
S.C. Code § 6-21-40