Sewage pump turning on without any sinks or toilet installed
Some systems are controlled by plc's programmable logic controllers that automatically pump every zone to make sure that a level sensor failure won't have your lower level floating in poop. I omit cyclic pumping or have with triple redundant sensors, I have seen 2 die but never all 3, it just may be the safety to prevent a very smelly situation. If it is a diagram sludge pump one than can pump almost solids ever firing if the pump makes some noise, you may not need this level of protection but if you do and it is not working things can go bad fast.