Tandem Health Family Medicine - Sumter. 319 N. Main Street, Sumter, SC 29150. 803.774.4500. ... patient portal. Locations. Contact. Careers. Tandem Health is a Health Center Program grantee under 42 U.S.C. 254b, and a deemed Public Health Service employee under 42 U.S.C. 233(g)-(n). A FTCA deemed facility..