Allegro36LA Black Tank

You have a 2022. I have had 3 Tiffins in the past 3 years that have NOT vented the black tank to the roof vent. ALL had the 2 toilets with the rear Macerator Toilet. They misplumbed the vent pipes. There was NO roof vent air pipe to the Black tank on these motorhomes. What you do is drain both tanks and then insert a water hose from the top roof/vents and see if any water goes into the black tank. If NO water goes into the black tank it is not plumbed to the roof vent. Doug

No, there are no partitions in any Motorhome holding tank. What you are experiencing is a vent issue. Next time you dump, have someone keep the manual toilet ball valve open. You can insert a paper towel cardboard tube to keep it open if the toilet has a electric ball valve. IF the tank then dumps normally, you have a tank vent issue. The purpose of a Macerator toilet is due to its location(usually in the rear of the motorhome), the debris has to be chopped and then power flush to the Black tank. Year model would help in this problem. Doug