If your toilet is running, it might be due to a faulty or broken flapper. The flapper is also known as a tank ball or flush valve. In case it’s faulty or broken, then you need to have it replaced.
A toilet can also run as a result of problems with the chain mechanism. If the chain is excessively long, it might get caught by the flapper. Consequently, the flapper will fail to close and cause the toilet to run. These problems can be fixed easily.