Drainage device for pile foundation drilling

The utility model relates to the technical field of pile foundation drilling, in particular to a drainage device for pile foundation drilling, which comprises a water storage tank, a tank cover, a water pump, an electric push rod and a filter plate, the tank cover is arranged at the top end of the water storage tank, and one side of the top end of the tank cover is in bolted connection with the water pump for pumping out accumulated water. By arranging a mounting frame, a grip and a sealing ring, when the filter plate needs to be replaced, the grip is held and pulled, and the mounting frame fixed on one side of the grip drives the filter plate to slide in the water storage tank along with the pulling of the grip until the filter plate is moved out of the water storage tank, so that the filter plate is replaced and cleaned; after cleaning is completed, the grip is held for pushing, the mounting frame drives the filter plate to slide in the water storage tank along with pushing of the grip, the filter plate is