Abstract: A rim seal is provided for a floating roof tank to fill the space between the floating roof and circumferential wall of the tank. The seal is a compressible toroid of approximately the diameter of the tank and has a cross-sectional diameter greater than the largest opening between the floating roof and the circumferential wall or an existing seal and the circumferential wall. An inner tube is provided which encapsulates the toroid; an outer tube is provided which is elastic and encapsulates the inner tube. Slits in the outer tube adjacent to the circumferential wall are disposed substantially circumferentially with respect to the toroid.