Repair a leaking toilet by straightening the guide rod, replacing the float ball, replacing the valve seat and replacing the flush valve assembly. The exact repairs depend on the specific cause of the problem.
Begin by inspecting the chain and guide rod located inside the toilet tank. Straighten the chain if twisted, and straighten the rod if bent.
A faulty float mechanism can also cause a toilet to leak. Test for this by pushing the float arm down to give the ball buoyancy. A ball that does not float immediately or that has water in it needs to be replaced to fix the problem.
Additionally, corrosion can prevent a stopper from closing, which can cause the toilet to leak. Lift the stopper, and inspect it for corrosion or blockage. Scour the stopper lightly if necessary. Replace the valve seat and stopper if severely damaged.
Finally, if these measures do not work, the flush valve assembly may need to be replaced. Bring your old flush valve assembly when purchasing a new one to ensure you get the right match. The shaft assembly also needs to be replaced if it is cracked or broken, so bring a replica of it as well.