S.C. Code § 6-11-990
For the payment of the principal and interest of all bonds issued pursuant to this article, as they respectively mature, and for the creation of such sinking fund as may be necessary therefor, the full faith, credit and taxing power of the special purpose district shall be irrevocably pledged, and there shall be levied annually by the auditor, and collected by the treasurer of the county in which the special purpose district is located, in the same manner as county taxes are levied and collected, a tax without limit on all taxable property in the special purpose district sufficient to pay the principal and interest of such bonds as they respectively mature and to create such sinking fund as may be necessary therefor. Such bonds may be additionally secured by a pledge of revenues derived from the undertaking to be financed and, if so additionally secured, the tax levy herein ordered shall be reduced to the extent that moneys for the payment of the principal or interest of such bonds shall be in the hands of the county treasurer on the occasion for the imposition of the tax levy herein otherwise ordered; provided, that the ad valorem tax levy shall also be reduced to the extent that there has been deposited with the county treasurer moneys derived from any revenues not pledged to additionally secure such bonds on the occasion in each year when the ad valorem tax levy is to be made, and in all instances where an annual tax levy is so reduced, the moneys derived from such unpledged revenues be applied to the payment of principal and interest of the bonds and to no other purpose.
S.C. Code § 6-11-990