South Carolina's Flagship University

Regulatory Pathfinder
for Coastal Development in South Carolina

Private Citizens: Additional Septic Tank Requirements

The Initial Treatment System must meet the following conditions:

  1. Each septic tank shall be designed and constructed to meet DHEC's minimum design and construction criteria;
  2. No septic tank can have a net liquid capacity of less than 890 gallons;
  3. There is a minimum capacity for septic tanks based on the number of bedrooms in the residence. For 2 or less bedrooms the tank needs to have a 890 gallon minimum net liquid capacity, for 3 or 4 bedrooms it must have a 1,000 gallon capacity, and for each additional bedroom beyond 4 the septic tank needs an additional 250 gallons of capacity. S.C. Code Regs. 61-56 Section VI(A).

An Alternate System must meet the construction criteria developed by DHEC for systems of its type and have a minimum repair area 50% the size of the original system. S.C. Code Regs. 61-56 Section V(F). An alternate system may be used if DHEC determines conditions warrant its use and has established appropriate standards for the system. S.C. Code Regs. 61-56 Section VI(B).

Final Treatment and Disposal Systems

In general:

  1. Distribution pipes to be used in individual sewage disposal systems must have written approval from DHEC prior to use. Approval is based on ASTM standards;
  2. DHEC must approve coarse aggregate material prior to use and the material shall be between 1/2 and 2 and 1/2 inches. Fines are prohibited;
  3. When DHEC determines it to be necessary distribution and drop boxes must be installed. If drop boxes are used they must be "stabilized by undisturbed or manually compacted earth and each soil absorption trench being fed through at least 2 feet of solid pipe prior to entering the coarse aggregate. The invert of the drop box overflow pipe shall be at the same elevation as the top of the coarse aggregate in the trenches fed by that box. Also, when utilizing serial distribution, the top of the coarse aggregate shall be level. Other methods that effect serial distribution, such as earthen dams, shall also overflow at the same elevation as the top of the coarse aggregate." S. C. Code Regs. 61-56 Section VII(A).

Conventional Trench Requirements

  1. At least 23 inches deep;
  2. Distribution pipe and trench bottoms shall be as level as possible with a slope of no more than inches per 100 linear feet from the beginning to the end of each trench;
  3. The trench bottom must be 18-36 inches wide and there must be 7 feet of undisturbed earth between trenches;
  4. At least 6 inches of coarse aggregate will be beneath each distribution pipe, 5 inches surrounding the pipe and 3 inches above it. The coarse aggregate shall be level across the trench width;
  5. DHEC shall determine the number, length and configuration of trenches based on the number of bedrooms or persons using the facilities and soil conditions;
  6. The coarse aggregate over the distribution pipe must be covered with a strong, untreated pervious material;
  7. No less than 9 inches of earth shall cover the coarse aggregate. S.C. Code Regs. Section VII(B).

Alternate Systems must meet DHEC standards for that type of system. S.C. Code Regs. Section VII(C).

Last Updated October 29, 2010


This project was supported through a generous grant from the South Carolina Sea Grant Consortium. The principal investigator is Professor Kim Diana Connolly at the University of South Carolina School of Law. Two law students, Keith Bartlett and Valerie Cochran, provided invaluable work toward project completion. Technical assistance with web design was provided by USC School of Law webmaster Tobias Brasier. Broken links should be reported to lawweb@law.sc.edu. This website is NOT intended as legal advice, and particularized analysis by professionals should be sought wherever appropriate.