tank material in manifold portion 34 regardless of which method is used for forming the duct system 35 it is important to have internally threaded steel nipples in the outlet ports to provide a positive seal with any components which may screwed into the port without the need for any o ring seals referring again to fig2 the tank 32 which is of substantially rectangular shape has end walls 38 and 40 and sidewalls 42 and 44 a bottom 46 is inclined diagonally across the tank 44 at an angle with respect to a horizontal plane to permit drainage of molten material in the tank from the highest corner of the bottom to the lowest corner of the bottom which is indicated in fig3 by a triangular low area 48 which also contains a circular pump recess 50 the recess 50 functions as a sump or collection recess from which a pump withdraws molten material as will be explained later in further detail as shown in fig2 and 3 a series of fins or ribs 52 extend vertically upward from the bottom 46 and are inclined at angles to direct the flow of molten material toward the low area 48 and the pump recess 50 as shown in fig3 a sinusoidal pattern of electrical resistance heating wires 54 are embedded inside the tank bottom 46 these wires are connected electrically in a know manner not shown to an electrical power source in the control.