On several Bs over the years I have found a spot under the body at the back of the coach where I could suspend (I used the galvanized pre punched strapping you can find any Lowes or HD electrical dept to suspend electrical conduit) from the chassis or something substantial a piece of four inch pvc pipe about two feet long. You can put a cap on one end and leave one end open. I would drill a quarter inch hole almost at the end of the opening.
Then, I would simply slink an extension or hose into the pipe and drop a clevis pin through the hole. You have to be a little imaginative and creative to find somewhere underneath to do this, but it is an easy solution. You have to make sure that it is positioned so it is not the lowest thing hanging down there.