I bought the Valterra HydroFlush for my 1/2 bath tank which doesn't have a flush on it. Problem is, there are turns to my piping between the sewer connection and tank. I don't see any appreciable amount of water making it back into the tank. If I had looked at my plumbing ahead of time, I would NOT have bought it.
I also imagine that there are very few tanks/plumbing setups that this would work for.
My RV is at the service center and one of the things they're doing is installing a tank flush onto that 1/2 bath tank.