Danny, That's what I have been doing. I'm in agreement that you can't drain it dry, so I'm leaving 5 gallons, 1/2 cup of Dawn, and a bottle of Calgon in it this year.
Elliott & Vicky, and Sadie the GSD copilot
2014 36RE, Onan, Titan disc brakes, 17.5 inch Sailun H tires, lots of other options
2013 RAM 3500 CC, LB, DRW, Cummins, AISIN, 4x4