This doesn't address the shower hose but recently had a small roof leak at my house where the toilet vent pipe goes thru the roof...
Went to local hardware store and found one of those three inch high and maybe 30-inches round plastic tubs that has a hose connection on it...
Very inexpensive... These are normally used to sit a water heater in it and give a way to trap water run off from a busted water heater

Google image
I got to thinking this would be perfect for using with the outside shower setup... You could run the drain hose away from the trailer into the grass somewhere...
Roy Ken
