Not every toilet leak creates a loud rushing sound. Many present as ghost flushing causes, where the toilet suddenly refills itself for six seconds at three in the morning without anyone touching the handle. This phantom cycling occurs because water is slowly escaping through a microscopic gap between the flapper and the flush valve seat.
To confirm whether water is sneaking past the primary seal, remove the tank lid and squeeze five drops of red or blue food coloring directly into the tank water. Do not flush. Step away for fifteen to twenty minutes. If colored water seeps into the toilet bowl, your flush valve seal has failed, confirming that water is bypassing the primary rubber barrier. If the bowl water remains crystal clear while the fill valve continues to hiss, the problem lies above: water is rising past the top of the overflow tube and dumping directly into the drain.
