[rohrmann]

I'm pretty sure your rig is plumbed, or should be, the same as ours. The black tank flush should be plumbed to the opposite end of the black tank from where the drain valve is located. Flush water should not flow out of the drain until you pull the black tank drain valve. Your rig, if it's the same as ours has the laundry drain cut in directly to the main drain line with no drain valves, so you must be connected to a sewer drain if you have a washing machine in your rig when doing laundry. Your grey tank is the water from the bath vanities and the shower, and this is the pull valve that is next to the black tank valve. Your galley tank is from the kitchen sink only, and that drain valve is behind the driver's side tires up on the side of the frame. I find it to be easier to access that pull with the rear drivers side slide in the out position.