A collapsible portable tank for storing liquids has a liquid impervious liner. The side walls of the liner are supported by a collapsible frame. A plurality of hand grips in a zigzag pattern on the floor panel of the liner facilitates manipulation of the liner to collapse the liner with the frame. The liner floor panel is of heavier material than the side walls and is heat sealed along its entire perimeter to the liner side walls, affording a more durable floor while eliminating clumsy excess liner material at the corners of the tank. Another hand grip on the floor panel opposite a drain in the liner side walls facilitates evacuation of stored liquid from the tank prior to collapsing the tank.