S.C. Code § 6-25-125
A joint system may fix, charge, and collect rents, rates, fees, and charges for its services. For so long as any bonds of a joint system are outstanding and unpaid, the rents, rates, fees, and charges must be fixed to provide revenues at least sufficient, together with other available funds, to pay all costs of and charges and expenses in connection with the proper operation and maintenance of its projects, and all necessary repairs, replacements, or renewals; to pay when due the principal of, premium, if any, and interest on all bonds payable from the revenues; to create and maintain reserves and comply with covenants as may be required by any resolution or trust agreement authorizing and securing bonds; and to pay any and all amounts which the joint system may be obligated to pay from the revenues by law or contract.
A pledge made by a joint system pursuant to this chapter is valid and binding from the date the pledge is made. The revenues, securities, and other monies so pledged and then held or thereafter received by the joint system or any fiduciary is immediately subject to the lien of the pledge without any physical delivery or further act, and the lien of the pledge is valid and binding as against all parties having claims of any kind in tort, contract, or otherwise against the authority or joint system without regard to whether the parties have notice.
S.C. Code § 6-25-125