Remove the tank lid and perform a visual inspection of the toilet flush valve to start addressing any issues or problems the toilet may be having. Adjust the flapper or tension chain to ensure the flush valve is able to form an effective seal. Drain the toilet tank and replace the flush valve to address a leaking flush valve.
Most flush valves utilize two components that allow operation of the handle to drain the toilet tank into the bowl. The flapper is a rubber seal in the base of the tank that is operated by the valve seat. Minor adjustments to the position of the flapper help to ensure the tank is filling properly. These adjustments can often be done by hand, or with simple household tools.
To completely replace a flush valve, shut off the water and hold down the handle until the tank is completely drained. Once the flapper is disconnected from the chain, it can then be removed. Check and sand the valve opening in order to remove any deposits that may keep the flapper from forming an effective seal. Inspect the flush valve to ensure proper operation once the new flapper is installed and connected to the chain.