<human>: What are the most common types of septic systems?
<bot>: The three most common types of septic systems are gravity flow, leach field, and active sewage treatment. Gravity-flow systems rely on the natural slope of the land to move the waste away from the home. Leach fields use a series of trenches or pipes to direct the waste into an underground soil absorption area. Active sewage treatment systems use an aerobic or anaerobic digestion process to break down the waste before it is released into the environment.