After I dump and rinse, I usually use the spray wand. While using the spray wand, or any other spraying system, the black water valve should be OPEN. The reason for this is, you want full spray pressure to hit the sides of the tank. Any water pooled in the tank will reduce the effectiveness of the sprayer.
You can try it with your kitchen sink.....spray water from your sprayer directly onto your hand. The. Half fill the sink with water. Put your hand at the bottom of the sink and spray your hand through the water. You'll feel a significant drop in pressure hitting your hand.
After spraying, close the valve. rinse your tank again, dump and you're good to go.
