URGENT HELP NEEDED - MAJOR SMELL FROM BATHROOM

marcarolle wrote:
I always use Camco orange RV black tank concentrated treatment after emptying both tanks. We started our stay on empty tanks.

The only time the grey / black tanks should be completely empty is when you winterize, otherwise never. Once you've dumped & flushed either you want to add a minimum 10% capacity of the tank with fresh water and tank chem of your preference which you'll then start your next camping trip with.