A method for disinfecting a water system of an aircraft includes letting-in of hot water at an inlet of the water system by a first ground service unit; flushing the hot water from the inlet, through water pipes of the water system, to an outlet of the water system; and letting-out of the hot water at the outlet, by the first ground service unit or a second ground service unit; the hot water being flushed into the inlet and out of the outlet over a predefined disinfection period; and the hot water being provided at the inlet via a continuous-flow heater of the first ground service unit.