PURPOSE: To provide high flexibility, hydrolysis resistance and burst resistance by forming corrugated portions to at least a part of a coolant conduit and mutually connecting the individual adjacent corrugated portions by at least one web.

CONSTITUTION: In a coolant conduit 1 comprising a plurality of polymer layers of different polymers compatible with one another at the contact surfaces of the layers, the conduit 1 has corrugated portions formed to at least a part thereof and the individual adjacent corrugated parts are mutually connected by at least one web, in this case, by three webs 2, 3, 4. This coolant conduit 1 can be produced by the coextrusion molding of a polymer to a pipe and suction molding succeeding thereto or the formation of the corrugated parts and the webs 2-4 due to suction molding. This conduit 1 has burst resistant strength enhanced by about 10-20% as compared with a conduit of the same system free from the webs 2-3 and not restricted in flexibility from a practical aspect.