S.C. Code Ann. § 29-3-30

Any person holding a lien by way of, or an interest in the nature of, a mortgage upon any property, the subject of taxation, upon which the mortgagor shall have failed to pay the tax or upon which there may exist a lien for taxes on any other property of the mortgagor, may at any time before the sale thereof for delinquent taxes, as provided in Title 12, pay the tax on all the property of the mortgagor, with any costs, penalties or assessments which may have accrued thereon, and thereupon he shall be entitled, as against the mortgagor, his representatives, privies or assigns, to include the amount so paid, and all interest thereafter accruing thereon, in the debt secured by the mortgage. And if a mortgagee pay such taxes he shall have a first lien on the property subject to such tax to the extent of the taxes so paid with interest from the date of payment.