Abstract: A drainage switch that can be used to extract and clean impurities is provided, which is mainly equipped with a set of elastic water stop plugs. The elastic water stop plug is composed of a main body around with elastic blocks, a pressure positioning piece, a lifting piece, and springs that are arranged inside the shaft tube of the main body, and a plug cap that is locked in the pressure positioning piece. The elastic blocks can be elastically against with a water pipe, so that the elastic water stop plug can be elastically clamped in a water pipe, which is easy to install and replace, and easy to take out and clean dirt.