The most common cause of toilet which continuously flushes is a flush valve seal malfunction. The flush valve needs to seal completely after each flush to keep water from leaking. When this seal fails, the toilet tank leaks water into the bowl continuously. This continuous flow of water triggers the fill sensors which then flush the toilet.
If you suspect the seal but aren’t sure how to confirm, we have an easy test for you. Simply put a few drops of food coloring into the toilet tank. If the colored water then appears in the bowl, you’ll have confirmation that the tank is leaking, and the valve needs to be replaced by a trusted A.J. Perri technician.