A running toilet can be a serious nuisance, especially if it flushes fine but just doesn’t know when to stop filling with water. Before you get started, take the lid off your toilet tank and flush the toilet several times. Pay attention to how all of the components in the tank work together. You should be able to pinpoint the issue with simple observation.
The most common culprit is a faulty flapper. This is a flap of plastic that looks like a drain cover. The flapper is attached to a chain that lifts it up when the toilet is flushed. This changes pressure inside the toilet, allowing dirty water to escape. After dirty water has been cleared from the toilet, the bowl and tank begin to fill. The tank is fitted with a special float that is designed to stop the tank from filling once it has reached a certain level.
If your toilet won’t stop running, check to see if the flapper is closing all the way. If it isn’t, figure out what the problem is and fix it. You might need to replace the chain or buy a new flapper. If the chain is getting caught under the flapper, shorten it so that this can’t happen again. If this doesn’t fix the problem, make sure that the valve is open all the way and adjust the float arm. If you discover that your toilet has faulty valves, rely on a professional to take care of repairs.