Abstract: This invention relates to an improved method of manufacturing a heat exchanger element. In a second aspect the invention concerns a heat exchanger element itself. In the third aspect the invention concerns a reservoir suitable for housing the heat exchanger element to form a heat exchanger. The element is manufactured by extruding polyethylene tubes and winding them into spiral coils. Each coil is located along the length of a rigid horizontal spacer bar in order to maintain even spacing of the coil. The element comprises a stack of coils which are not restrained against vertical movement. The element also comprises a cylindrical void through the center.