For the last few years when winterizing I always wound up using a compressor to blow out the water in the black tank flusher/rinser lines because the back flow valve just won't allow you to pour antifreeze down into the fitting.
While winterizing this year it dawned on me that I could just use the blue curly plastic hose for the outside shower for this task. Take off the hose nozzle and screw the male fitting into the flush water inlet connector and the other end connected to the shower fitting, then with the gallon of antifreeze still connected to the water pump all I had to do was turn on the outside shower for a bit and wallah nice pink antifreeze ran through the line.
And on my 245rks the outside shower assembly is just two inches below the flush inlet connector...Duhhh...why didn't I think of that before!!
Ron W.