If you properly maintain your black tank and RV toilet seal, your RV should never smell like a sewer—but if it does, start by completely emptying your black tank. If the waste is not emptying out of the sewer hose, you most likely have a clog. Use an auger to remove the blockage and then completely empty the tank. Follow with a black tank flush if your RV has that feature. Then add plenty of fresh water and RV black tank chemical. Check the RV toilet seal to make sure it is well-lubricated and holding water in the toilet bowl. It should create an airtight seal that prevents odors from escaping the black tank into the RV. If the toilet seal is cracked or damaged, replace it with a new one. If your RV is still smelly, you may have a leak where the pipe from the toilet connects to the top of the black tank or an air leak in the black tank vent piping. Lastly, don’t overlook odors that can come from the gray tank. Remember to regularly empty and clean your gray tank as well.