A method and apparatus for insulating a fluid line in a container configured to contain a fluid. The apparatus comprises a container, a fluid line in the container, and a tube. The container is configured to contain a fluid. The tube is placed around the fluid line in the container to form a channel around a first portion of the fluid line. The tube is configured to contain the fluid from the container in the channel and to prevent a first flow of the fluid between the container and the channel except through a number of ends of the tube. The tube is further configured to reduce a second flow of the fluid within the channel such that the fluid in the channel insulates the fluid line.