After unsuccessfully "listening" for leaks and "watching for soap bubbles", I tried a suggestion that I read on another website. Placing a wet piece of plastic wrap (I used Glad Wrap) over the ring, a leak will cause the plastic to blow up from the ring. Use a sheet about 18" long, and work your way around. Worked like a charm and quickly found the leak. I temporarily stuck a piece of duct tape on it until I get supplies for a more permanent repair.