Myth No.9: We have a sagged line from the house to the tank, it shouldn't cause any issues for blockage
Sagged lines are a common occurrence as ground settles overtime and inlet lines will lose their positive grade creating a "belly" or a sag. Some sags are worse than others but a full sag of the 4 inch diameter pipe means the toilet paper and solids have a ramp to try to run-up to get into the septic tank.
Sags in the inlet line are more crucial to repair than one on the outlet side of the tank. Keep in mind the inlet side has both solids and liquids within. The ramp created by a dip in the pipe makes it hard for paper to freely flow into the tank.
Should this ramp back up with a clog of paper, you guessed it; it's heading back to the last place you want it. Directly into the house.