Abstract: A drain system for the floating roof of an oil tank or similar tank couples a drain sump at the underside of a central portion of the floating roof to the outside of the tank wall at a lower portion thereof via a flexible arrangement of rigid pipe lengths joined together by swivel joints. Each swivel joint is made pivotable about an single axis by a pair of side frames having pairs of leg portions pivotally coupled to each other along the axis and mounting a length of flexible pipe therebetween. The opposite ends of the length of flexible pipe are coupled to an opposite pair of pipe couplings mounted on central portions of the side frames between the leg portions and adapted to be coupled to the lengths of rigid pipe. The length of flexible pipe which is comprised of a length of flexible hose disposed between inner and outer wire helices is coupled to the pipe couplings by arrangements which include swedges, swedge rings and collars.