Does your toilet sound like it’s flushing itself? No, it isn’t because there is a ghost in your bathroom. However, it may be because of one of these 2 main reasons (Angie’s List):
1. Water is leaking from the tank: If water is escaping from the tank into the bowl, the water level in the bowl will obviously rise. This causes the toilet to flush itself, or “siphon.” How do you begin tackling this issue? First change the flapper or adjust the water level. This may be a job for you or your plumber.
2. Debris or damage: There may be damage to or debris in your flush assembly or fill valve. This causes the toilet to “run” or make that flushing sound. If you can not find where the damage or debris is, consult your plumber. In all instances of toilets running, it is likely that something needs to be fixed.