Each has its own advantages, depending on customer choice.

Single tube in series, the way is simple, save pipe. But the radiator (especially the most end) should be increased accordingly, the temperature of each room can not be individually adjusted and closed, the system resistance, and require high boiler water temperature.

Double pipe in parallel, the connection is relatively complex, but for each group of radiator regulation is very convenient. Usually the trunk pipe is arranged at the top of the room, and each radiator is connected with the horizontal main pipe by the vertical branch pipe, and the system is convenient to adjust and overhaul. The problem is too much indoor pipeline, affecting the decoration, the system is not easy to discharge air, easy to produce pipe flow noise.