The ornamental design for a hot waterradiator for use in a hot waterheatingsystem, as shown and described.
FIG. 1 is a front, elevational view of a hot water radiator for use in a hot water heating system showing the new design;
FIG. 2 is an top view of the hot water radiator for use in a hot water heating system shown in FIG. 1;
FIG. 3 is a bottom view of the hot water radiator for use in a hot water heating system shown in FIG. 1;
FIG. 4 is a right side, elevational view of the hot water radiator for use in a hot water heating system shown in FIG. 1 (the left side, elevational view of the invention is a mirror image of the right, side elevational view shown in FIG. 4); and,
FIG. 5 is a perspective view of the hot water radiator for use in a hot water heating system shown in FIG. 1.