In the 36FL the bath & shower facilities, kitchen sink, dishwasher all drain into the galley tank. If you have a washer that drains into the other grey tank. If you do not have a washer you are hauling around a 45 gallon grey tank that does nothing!!! To improve our grey tank capacity, I installed a waste water valve in our sewer boom (we have a 2012 36FL) and keep that valve closed and open both grey tank valves allowing the water to "cross level" so that we have 90 gallons of grey water capacity.
John and "Sam"