Over the winter I installed a 6x6 vinyl fence post between the rails of the camper to store the drain hose... the fitting fits in the post with the hose now.
Before our current setup, we stored the hose in the bumper and the fittings in a plastic WalMart bag in our storage compartment.
Like MegaJohn, I use the vinyl fence post. I mounted it on top of my existing bumper. Actually, I just strapped it to the bumper so I didn't have to drill any holes. Holds all my hoses, and the 90* fitting. Used fence caps on both ends. Drilled holes for any water to run out and put hinges and thumb screw on access end.
On my new TT, I glued a 4" sewer cleanout to a closet (toilet) flange, painted it black, and bolted it to the backside of the crosswise frame member at the back of the A frame outboard of the I-beam. I just screw the thing into it. When I get the trailer back from the dealer so I can take some pictures, you will see this mod in the DIY forum.
Note: I am using the Valterra sewer adapter. The angled portion has the threads. The hose has no angle on it at all. The hose is like an extension hose that way, and I can hook as many of them together as I want in any order and only have one 90 degree angle (the sewer adapter). I could set up a 100' dump hose if I wanted! BTW: I am using the Valterra Viper hose. It is not like a slinky -- where you compress it and it immediately uncompresses on you. With it and the Camco Rhino-Flex, when you compress them, they stay compressed. Kind of reminds me of the straws with the accordian bend setup in them.