A toilet flushing system includes a fresh water feed, a fluid storage container connected to the fresh water feed, and a supply line coupled to the storage container and a toilet. The fluid storage container has a container casing and first and second separating diaphragms within the casing. The separating diaphragms define first, second and third partial chambers within the container casing for separately receiving gas and fresh water. The second partial chamber is defined between the separating diaphragms and receives gas. A valve in the fresh water feed and the supply line, closes the fresh water feed and the supply line. The valve is movable between a first switch position for filling the partial chamber with fresh water to be delivered to the toilet and a second switch position in which the third partial chamber simultaneously is filled with a medium.