I'm having the same problem. It seems that the dishwasher (kenmore) pumps out the water so quickly that it overloads the 'drain' part or the air gap system. I'm wondering if I avoid the airgap (go direct diswasher to disposal) or if that would violate California code or cause problems with waste water getting into the dishwasher through the exit line...doesn't seem like it should if the line is elevated above the disposal intake.