We just purchased a used 2017 315RLTS from a private party and I'm trying to get the black tank cleaned out. The built-in black tank flush is nice and will be fine in the long run but I was hoping to speed things up so tried to use my wand with the rotating nozzle by sticking it down the toilet. I was able to go down the drain pipe but was stymied by what looked like a metal cross member just an inch or two below the toilet drain pipe. Nothing I tried let me past it. It looks like anything flushed down the toilet will hit that instead of going into (and hopefully floating in) the tank itself.

Does anyone have a schematic of how the tank and its inlets/outlets are laid out? Is this just an elbow? Any insights appreciated!