<human>: What are some of the most popular types of septic tanks?
<bot>: Some of the most popular types of septic tanks include gravity-fed, pressure-assisted, and vacuum-assist systems. Gravity-fed systems rely on a pipe that runs from the septic tank to the drain field. Pressure-assisted systems use a pump to move liquid waste through the pipes. Vacuum-assist systems work by using suction to draw waste into the system.