PURPOSE: To provide a heat insulating pipe system able to restrain lowering of the temperature of hot water or water remaining in the inside, and having durability in a feed hot water pipe or a feed water pipe.

CONSTITUTION: An inner pipe 2 is inserted in a feed hot water pipe or a feed water pipe 1. Expanded parts 5, 6 so expanded as to increase the diameter of the pipe are provided near both ends 3, 4 of the feed hot water pipe or the feed water pipe 1, and projecting parts 7, 8 projecting in the acute angle direction in relation to the axis of the feed hot water pipe or the feed water pipe l are integrally provided on the expanded parts 5, 6. Both ends opening parts 9, 10 of the inner pipe 2 inserted in the feed hot water pipe or the feed water pipe 1 are so arranged as to penetrate the projecting parts 7, 8, and the clearance parts between the projecting parts 7, 8 and the inner pipe 2 are blocked by sockets 11, 12.