Does anyone know a trick to emptying your black tank completely? We also notices an odor when we are unable to hook up to sewer. We use the dropins, but not helping the odor over 3-4 days.
Depends where you are dumping at. If you are dumping where it's level not everything on the bottom will drain out. Which is why you should always (if possible) after dumping to fill with water and dump again.
If you are at a CG just raise the opposite side of your RV with levelers. Then fill with water and dump and keep filling with water and then dumping a few times. That should clean out the bottom of your tank.