Abstract: An automatic flushing system for use with toilets or urinals which includes a tank having a siphon outlet and a hollow float which has a water access port and an air access port. There is also provided support means for supporting the float for generally vertical movement within the tank. There is also provided a tank inlet and tank inlet valve means which is operated by the support means for controlling flow of water through the tank inlet. There is also provided air access port valve means for controlling flow of air into the float. The support means is suitably characterized to enable the float to reach the intermediate holding level which is lower than the maximum level within the tank. The air access port valve means may also control flow of air through the air access port in such a manner as to provide a water seal associated therewith and a gas lock in the hollow float.