can for example reach a tapping point 70 which can be actuated via a tapping point valve 71 a tapping point of this type may for example be a water tap a toilet flush a showering or bathing means or a cooking means further a water inlet pipe 73 may be provided via which for example the water reservoir 10 can be filled this filling may take place either via the bypass pipe 37 when the bypass valve 38 is open or else by a backwards flow through the pump 30 however the pipe 73 may also be used so as to release all of the water in the fresh water system for example when cleaning or maintenance cycles are being carried out via a corresponding circulation terminal 16 the water supply pipe 72 can be passed back into the water reservoir in this context the circulation pipe may discharge both above and below the water level moreover the water reservoir may comprise a negative pressure valve 15 which for example prevents the pump from generating a negative pressure which can lead to the water reservoir collapsing in the water reservoir when there is no bleed air pressure loading and the pump 30 is running this may occur if for example the bleed air supply system is inactive during aircraft maintenance operations on the ground but the water system is intended to.