I found some interesting information on the DHEC website, that serves as a good overview for South Carolinians.
South Carolina households generate nearly 3 billion gallons of sewage each year. About 60 percent of homes are served by public or community sewer systems. The rest — more than 1 million households — rely on septic tanks located on their property.
Well designed, well-maintained septic tank systems use nature — bacteria and soil — to break down and filter the waste we flush and rinse away. They can be the safest, most cost-efficient way to treat wastewater.
But a leaky, clogged or damaged septic system can:
In an average year, 10 to 30 percent of septic systems fail to work properly, usually because of poor maintenance. Don't let yours be one of them — learn how your septic system works and how to care for it