It might be overkill, but I flush the tanks and use Dawn/Calgon after every trip. I have a built-in tank flusher so I hook that up and let it do its thing. I also allow the black tank to fill almost full several times and then dump it. Once I have only clear water coming out of the black tank, I let it empty as much as it will, and then close the valves, and put in two gallons of hot water mixed with a box of Calgon and 1 small bottle of Dawn. So far, so good.....no smells inside, and everything appears to be working properly. Unfortunately, my tank sensors were out of service long before I got the rig.