To prevent degradation in closing effect even if garbage or the like is adhered to openings of service water holes.

Packing members 105A, 105B which are in close-contact with opening end faces of service water holes are attached to closing valves 100A, 100B which close the service water holes 73A, 73B to which tap water (service water) is supplied. Elastic bodies such as rubber whose area is larger than that of the opening end face are used for the packing members. When the closing valves are closed in a state that the garbages mixed into the tap water are adhered to the opening end faces, the packing members close the opening end faces by the elasticity of the packing members with the garbage adhered thereto. Clearances caused by the garbage on the opening end faces are closed, so that the elevation of a sewage water surface is suppressed.