Abstract: A method for making a liquid storage tank for holding chemicals and heating oil and water and liquids compatible with high-density polyethylene. The tank is lap welded with a perforation in the lap weld and contains a molded polyethylene lining inside the tank.

Abstract: A vessel for liquid storage comprising a shell and an end element enclosing each end of the shell. The end elements have a central region which is generally planar but which can be provided with indentations for strengthening purposes. The end elements have a peripheral flange comprising a continuous U-shaped channel. The end elements are mounted on the shell so that the outer arm of the U-shaped channel abuts the interior wall of the shell and so that the concave surface of the U-shaped channel faces the interior of the shell so that the outer arm forms a lap joint with the shell. A fillet weld secures the lap joint.