Water disinfection system comprising a water disinfection device (10), having a UV light generator (13, 14) for the UV treatment of water, and a water pipe (82, 81), having a first pipe portion (81) and a second pipe portion (82) and a third pipe portion (83) which branches off between the first and the second pipe portion, wherein the water disinfection device comprises a first water connection (11) and a second water connection (12), wherein the first water connection is connected to the first pipe portion (81), wherein the second water connection is connectable to a water reservoir (60) which is to be provided, wherein the second pipe portion is connectable to a water source (90) which is to be attached, wherein the third pipe portion is connectable to a tap (70) for water, so as to be able in this way to provide an improvement in the water quality