<human>: Which are the most common types of septic systems?
<bot>: The most common types of septic systems include gravity-based, pressure-assisted, and aerobic treatment systems. Gravity-based systems rely on natural forces such as gravity to move waste from the home to a septic tank, while pressure-assisted systems use pumps to move waste through the system. Aerobic treatment systems use bacteria to break down waste in an enclosed container before it is discharged into the soil.