They're common used in multi stage septic systems that have a perc field above the tank level. If this pump is without power for a significant time, it will cau

They're common used in multi stage septic systems that have a perc field above the tank level. If this pump is without power for a significant time, it will cause quite a problem. However usually your tank will have enough free capacity for some hours. You don't see pumps in single tanks very often due to solids blocking the intake.