The drain lines carry waste from various fixtures. The vents provide air pressure that allows the waste to flow freely. The main waste line carries the waste to the sewer system and is the most likely area for clogs to occur. Familiarize yourself with the main cleanout, a sealed opening that can be unsealed to allow access to the inside of the drain line. A bed of gravel under the leach field allows the liquid to settle into the ground.
Most septic systems are below ground and fed by gravity.
Mound systems are used in some low-lying areas. In these systems, a grinder pump turns solid waste into sludge before pumping it into the septic system. Garbage disposals can be used with septic systems, but no heavy grease should be sent through them. Avoid pouring harsh chemicals into drains leading to a septic system. The cleanout for the septic system should be located within 5' of the house.