Don, we use Blue Dawn(1 cap) and liquid Calgon(2 caps), using the Calgon bottle cap.. We also have used most everything out there without success.. We have never had a problem with odors from the gray tank but have with the Black tank.. I would suggest, if you haven't already, you install one of the rotating vents for, at least, the Black tank.. We got the metal one,can't remember the name, but it took away almost all of the odor, except while flushing..
Mike M..