Do you have a toilet running continuously? You may be surprised to know that there are many reasons why toilets run continuously. Find out what causes them here! Toilets can sometimes run continuously for no apparent reason. This condition is called "toilet tank overflow." It can happen when the water level in the tank drops below the float valve. The float valve opens the drain line, allowing water to flow into the bowl. The Tank Is Empty. If the tank is empty, then the float valve will open the drain line. Water will flow into the bowl until the water level rises above the float valve. Once the water reaches the top of the float valve, the float valve closes again. The Flapper Valve Is Broken. A flapper valve is a type of check valve used in plumbing systems. They are designed to prevent backflow of water when the system is turned off. This prevents sewage from backing up into the house. There Are Too Many People Using The Bathroom. If you notice that the bathroom is being ...