I don't have one but I would think blowing out the trailers water lines should do the trick. That is how we winterize the one in my sons barn up at his campground. I don't remember any kind of drain on it.
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine