To install more of a header single body and to make the header single body rotatable, in heat insulating material for a header constituted by sequentially connecting header single bodies.

The header single body has a penetration flow passage part which is connected with a main pipe for water supply/hot water supply and whose outer cross section is circular, and a branched part extending from the flow passage part at right angle. In the heat insulating material for the header constituted by using the header single bodies and connecting the penetration flow passage parts, the heat insulating material is divided into two at a position dividing the penetration passage part from the branched part of the header single body, a recess part holding the header single body is formed therein to mold a insulating material base, the outer cross section of the heat insulating material of a part wrapping up at least both sides of the penetration flow passage part is a cylindrical shape of circular shape concentrically with the penetration flow passage part, and one end of the cylinder constitutes a enlarged diameter part to which an outer shape of the other cylindrical shape is fit. In the figure, 20 is the heat insulating material, 21a, 21b are the heat insulating material base, 22 is a recess part, 23 is the circular cylindrical shape part constituting the circular shape concentrically with the penetration flow passage part, and 24 is the enlarged diameter part.