PURPOSE: To facilitate works for piping and to eliminate a restriction in a mounting space.

CONSTITUTION: A pipe connection port 2 is composed by coupling its inner tube 4 to a return port 6 in a connector and its outer tube 5 to a forward port 7 in the connector. A pipe connector 3 for connecting an outer tube is coupled to the port 2. The connector 3 has a double tube structure having an inner cylindrical tube 8 and an outer cylindrical tube 9. The tube 8 is connected to the tube 4 and the tube 9 is connected to the tube 5 by coupling means. The connector 3 further has a first connection tube 10 extended from the tube 4 and a second connection tube 11 extended from the tube 9. Two external tubes are coupled to the connector 3. Further, the connector 3 is so formed as to be rotatable around the central axis of the port 2.