Our Jayco has a sewer hose storage cubby. Uses this door
and a piece of PVC pipe with a cap on the inboard end.
The length of hose it can store depends on how long a pipe you can install without hitting some component of frame or body. In our case, it'll hold the 5-or-so-foot hose we use at dump stations. Not a solution for a longer hose without a different installation site.
You can also buy various storage tubes, just gOOgle "rv sewer hose storage" or you can make something with PVC Pipe or maybe a PVC Fence Post. A 6" PVC post would hold your hose with couplers on its ends. Might be easier to mount a square tube than a round pipe.
Not the best idea to store the hose in a square tube steel bumper anyway. Really promotes RUST and it doesn't take much for them to rust through.
