To assure a necessary flow rate and to reduce in size by providing a pair of second passages across first passage, and providing a third passage parallel to the first passage across the second passage between openings of one side of opposed surfaces.

A part of warm water fed from a feed pipe 102a to an opening 3b is fed to a warm water pipe 105a of a floor heating panel 104. The other part of the water fed to the opening 3b is fed to a warm water pipe 105b of the panel 104. Thus, the water fed from right to left of the panel 104 through the pipe 105a is fed to an opening 2t through a joint 10. Similarly, the water fed through the pipe 105b is fed from the joint 10 to an opening 6, and fed to the opening 2t through a second passage 7t. Thus, the waters circulated from both the pipes 105a and 105b to the opening 2t are combined. The combined waters are fed separately to a first passage 4r and a third passage 8, again combined to the opening 2b, fed to a circulating pipe 102b, and circulated to a heat source machine through a header.