To reduce the water hammer at a low cost by forming a cross sectional area of a branch connection part so as to be gradually increased toward a main body tube.

In the case where the pressure wave generated in one water cock is transmitted to connection parts connected to a main body tube 1, namely branch connection parts 3a, through a branch tube 5, since these branch connection parts 3a are formed so that the cross sectional area thereof is gradually increased toward a header body 1, the pressure wave is damped in these connection parts 3a,..., and reflected variable is lowered. On the other hand, the pressure wave entered into the header body 1 is damped by the volume expansion of the water inside of the header body 1. Since the pressure wave transmitted from the water cock to the header body 1 through the branch tubes 5a,... is damped at the connection parts 3a,... and inside of the header body 1, the pressure wave to be reflected by the header body 1 so as to be transmitted to a water cock side is reduced, and water hammer is thereby lowered. Pressure wave can be lowered more by connecting a pressure buffer device 9 to the main body tube 1.