This paper describes an electrification of transient flow of pure water in a PFA (PerFluoroAlkoxyethylene) tube. Pure water flowing slowly in a PFA tube is electrified positively, negative charges are left on surface of the PFA tube. However, our experiment clearly shows that water flow in high Reynolds number condition carries negative charges on its head, which results in a negative high potential. The subsequent part of water flow electrified positively like the slow flow. These negative and positive electrifications depend on the water flow velocity as well as the tube length and the initial residual charge on the PFA tube. Our experimental results implies that the head of water flow plows the residual negative charges on the PFA tube and are confined to the head by splitting apart. Two-phase water flow causes the negative electrification phenomenon.