I have a North Country TT. It does not seem to drain the blackwater tank completely. I have taken it in once and they removed the two "cut outs" that had fallen into the tank during construciton but it still does not appear to drain right. In other travel trailers I have had, when you opened the valve the blackwater would rush out. You could hear the flow of the water. That is how the gray water tank sounds as well. When I open the blackwater tank it comes out very slowly and never gets completely emptied. I can open the toilet valve and look down in the tank with a flashlight and still see blackwater. I would think I would see an empty tank. Any thoughts or advice?? Thanks