A fill valve system with a float nested in a container connected to the fill valve and a siphon device passing water out of the container into the toilet tank, with the siphon device having an air vent dimensioned such that: (i) tank refilling is delayed until after the flush valve closes; (ii) the fill valve is not turned on by small leaks in the tank; and (iii) the fill valve turns off when it encounters large leaks in the tank.