Device for the contamination-free filling of a tank from a canister having a. a tank adapter with - a tank fastening flange for fastening to the tank, and - a first coupling part, and with - a closable connecting channel, b. a canister adapter with - a canister fastening flange for fastening to the canister, and - a second coupling part, and - a closing piston which is guided in the canister adapter and which closing piston can be adjusted between the open position and the closed position via an actuating element, and - the closing piston has an inner channel which provides a fluid connection between the flushing connector and the canister fastening flange in the open position of the device, the tank adapter and the canister adapter being connected releasably to one another via the first and the second coupling parts (301, 401), and the closing piston having a first contact face which is in operative contact with a second contact face which is provided on the tank adapter when the second coupling part of the canister adapter is coupled to the first coupling part of the tank adapter, and having c. a flushing connector for feeding in cleaning liquid, which flushing connector is attached to the tank adapter and is connected to the closable connecting channel, - the device providing a fluid connection between the canister fastening flange and the tank fastening flange in an open position and closing the fluid connection between the canister fastening flange and the tank fastening flange in a closed position, and - it being possible for the second contact face to be raised up from the first contact face, while the second coupling part of the canister adapter is coupled to the first coupling part of the tank adapter. a. a tank adapter with - a tank fastening flange for fastening to the tank, and - a first coupling part, and with - a closable connecting channel, - a tank fastening flange for fastening to the tank, and - a first coupling part, and with - a closable connecting channel, b. a canister adapter with - a canister fastening flange for fastening to the canister, and - a second coupling part, and - a closing piston which is guided in the canister adapter and which closing piston can be adjusted between the open position and the closed position via an actuating element, and - the closing piston has an inner channel which provides a fluid connection between the flushing connector and the canister fastening flange in the open position of the device, the tank adapter and the canister adapter being connected releasably to one another via the first and the second coupling parts (301, 401), and the closing piston having a first contact face which is in operative contact with a second contact face which is provided on the tank adapter when the second coupling part of the canister adapter is coupled to the first coupling part of the tank adapter, and having - a canister fastening flange for fastening to the canister, and - a second coupling part, and - a closing piston which is guided in the canister adapter and which closing piston can be adjusted between the open position and the closed position via an actuating element, and - the closing piston has an inner channel which provides a fluid connection between the flushing connector and the canister fastening flange in the open position of the device, c. a flushing connector for feeding in cleaning liquid, which flushing connector is attached to the tank adapter and is connected to the closable connecting channel, - the device providing a fluid connection between the canister fastening flange and the tank fastening flange in an open position and closing the fluid connection between the canister fastening flange and the tank fastening flange in a closed position, and - it being possible for the second contact face to be raised up from the first contact face, while the second coupling part of the canister adapter is coupled to the first coupling part of the tank adapter. - the device providing a fluid connection between the canister fastening flange and the tank fastening flange in an open position and closing the fluid connection between the canister fastening flange and the tank fastening flange in a closed position, and - it being possible for the second contact face to be raised up from the first contact face, while the second coupling part of the canister adapter is coupled to the first coupling part of the tank adapter.