An adapter for a drain device, for installation in a floor panel, and having a receptacle with an upper inlet opening through which waste water can flow into the drain device, and parts which can be connected in a fluidic manner to a drain pipe and the receptacle, so that waste water which has passed through the inlet opening can enter the drain pipe. To improve the sealing function, the adapter has a base part having an inner thread, a first coupling point to the drain pipe, a second coupling point to the receptacle and which couples the receptacle to the drain pipe, a sealing ring that can be installed in the base part to seal the adapter from the drain pipe, and a compression ring with an outer thread compatible to the inner thread of the base part for exerting a compressive force on the sealing ring.