A disinfecting and cleaning agent connection device for devices with a chamber for the holding or transport of fluids has a connection line that connects the fluid chamber with a disinfecting or cleaning agent container. The connection device has a connection line, a buffer chamber, a sealing element in the upper section of the buffer chamber connecting it with the fluid chamber, a channel which opens into the bottom section of the buffer chamber and has a siphon-type section whose end lies lower than the bottom of the buffer chamber, and a fluid sensor in the buffer chamber which is lower than the upper section of the siphon area and higher than the channel opening into the buffer chamber. The disinfecting and cleaning agent connection device can be used in conjunction with medical devices such as a dialysis machine and a reverse osmosis machine.