My Miramar has 1 black and 1 grey tank. If your black tank empties and your bathrooms does not have sewer odors, I think your roof vent is good. I am wondering if your gray waste system has a physical clog preventing water to drain Into the tank. The other possibility is the tank is full and you can not empty the wastewater. Thor Customer Service has blueprints for your motorhome model. They will email copies to you.
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