Septic System problems generally fall into three categories:

Improper system sizing, a septic tank that is too small can easily be overloaded and cause septic system failure. Systems are designed for a specific amount of water and if the water usage exceeds the design perimeters a failure is eminent. Too little drainfield will cause saturated soils and system failure.

Clean water infiltration, reducing clean water infiltration clean water which does not require septic treatment can overload your septic tank causing wastewater to flow through the tank before it is treated. The most common is leaking stools. Extreme overloading can wash solids into the absorption field and plug the soil pores. Do not route water from sump pumps through the septic system; pump it outside the house. Divert surface drainage and run off from roofs away from the soil absorption field area so the soil will not become saturated.

Lack of proper system maintenance.
Pump septic tanks every 3 to 5 years depending on the size and the amount of wastes entering the system. Pumping is needed if the tank is more than one-third full of sludge or if the scum buildup is more than 12 inches thick. Methane gas, a dangerous explosive, and hydrogen sulfide, a toxic gas that can cause asphyxiation, both may be present in your septic tank. A professional septic tank cleaner has the experience, equipment to pump your tank safely and dispose of the sludge.

Older septic systems may be overloaded because of modernization of family living style or change in family size. Dishwashers, automatic washing machines, water softeners, and garbage disposal units require additional water and wastewater treatment. If a septic system is too small, waste moves through the septic tank too fast for sludge to settle and bacteria to break it down. This may cause solids to enter the absorption field and plug up soil pores, thus causing the system to back up. 
R. Chris Howie & Darin R. Howie
2009 Rapid City Business of the Year !