The flow of piped medium in the direction opposite to normal flow is called backflow. It is caused by a difference in water pressures. Backflow is normally prevented by a non-return valve, and sometimes a gooseneck on the pipe system. In the pictured system, only the gooseneck will prevent backflow into the basement.
Grundfos pumps for domestic, commercial or municipal water supply and wastewater systems can be installed in systems designed to avoid water backflow and wastewater backflow.