I am building a tank in tank. I am pulling water from directly above the firebox. I am returning it on the side about half way up the tank at the back. I am adding an elbow to the inside of my return that will direct the return water to the back bottom corner. I was wondering about adding a pipe inside the tank that would run next to the firebox and go from one end of the tank to the other. My thinking being that the water heating up in that pipe would then push out the ends and help circulation. Ideas?