To provide a hot water storage tank capable of keeping a predetermined heat insulating performance and reducing its manufacturing cost, and a molding method of a heat insulator for the hot water storage tank.
A front side heat insulator 14 and a rear side heat insulator 15 are composed of first heat insulators 14a, 15a with foaming magnification of 50 times and second heat insulators 14b, 15b formed to have thickness dimensions smaller than those of the first heat insulators 14a, 15a and made of synthetic resin with foaming magnification of 30-40 times. The second heat insulators 14b, 15b with the foaming magnification different from that of the first heat insulators 14a, 15a and having high heat insulating performance are used for parts with smaller thickness dimensions in the front side heat insulator 14 and the rear side heat insulator 15. Necessary heat insulating performance can be obtained thereby without using expensive heat insulators such as vacuum heat insulators, and the predetermined heat insulating performance can be kept while the manufacturing cost can be reduced.
YU AKITO
Yukio Nagauchi
Junichiro Yanagi