A water disinfection system includes a water disinfection device, having a UV light generator for the UV treatment of water, and a water pipe, having a first pipe portion and a second pipe portion and a third pipe portion which branches off between the first and the second pipe portion. The water disinfection device includes a first water connection and a second water connection. The first water connection is connected to the first pipe portion. The second water connection is connectable to a water reservoir which is to be provided. The second pipe portion is connectable to a water source which is to be attached. The third pipe portion is connectable to a tap for water, so as to be able in this way to provide an improvement in the water quality.