The supply and return lines connect to the angled tubes attached to the fitting that is the "lid" of the fuel tank. You must remove those to get the pre-pump unit high enough out of the tank to access the small hose on the pre-pump that rots and allows air into the system. If you drop the tank, the unit could be taken far enough out of the tank to replace the pre-pump hose (with difficulty I imagine) without removing the supply and return lines. However it's much easier to loosen the clamps and remove the two hoses than to drop the tank.