An experimental investigation on gas and liquid separation at Y-junction tubes was conducted to explore whether it is viable to keep Y-junctions in good operational condition by pressure control. In the experiments, four junctions were combined in series, all with a 60 degrees upward branch. The results show that there exists a critical value for the pressure drop ratio to make the system perform best, and the pressures at the inlet and both outlets play a significant role in the separation efficiency. Furthermore, a new relationship has been developed for the prediction of the phase split at Y-junction tubes.