I believe the controller actually switches the ground rather than the hot, though I never understood why.
It will be located at the closest convenient point to where the wires from the various switches converge on their way to the pump. That is almost never near any of the actual switches. My technique has always been to start at the pump and work backwards, since odds are the controller is near the pump than any of the switches, but that's just my limited experience. With one switch in the galley and another one or two typically in the bath area, the closest point for the wires to converge is usually somewhere in between bath and the pump, which is often located not far below the bath area. But you have to evaluate based on the actual locations of switches and pump in each rig.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL