We have a Thor 2017 Freedom Elite 26HE. In addition to the black and gray levers on one side of the RV there is another lever on the other side. We can't find any info on what this lever is for. We only discovered it about 6 months after we bought the RV. We've asked 3 different service people and they don't know.? One person suggested pulling it out when we dump.
My 28z has a 3rd lever located on the passenger side and it is the 2nd black tank lever. I open the black tank lever on the drivers side then open the lever on the passenger side, close them when emptied and then empty the gray water. Under the MH you will see the black tank drain tube go across from one side to the other