A toilet tank that trickles water slowly not only can create an annoying sound, but it also wastes water and increases your monthly water bill. Usually the cause of a toilet that has a constant trickle is a worn-out flapper valve, which is the large rubber cap that sits over the pipe that leads to the toilet's bowl. Sometimes the chain that connects the flapper valve to the toilet's handle can become kinked or is adjusted so it is too short, not allowing the flapper valve to sit down tightly over the pipe below.
Close the water supply valve for the toilet's tank by twisting the handle clockwise as far as possible. Flush the toilet once to drain most of the water from the tank.
Cut the old flapper valve with a utility knife, cutting away the pieces of the flapper that connect to the overflow tube. Remove the hook from the top of the old flapper valve. The hook is on the end of the toilet handle's chain.
Position the tabs on the end of the new flapper valve over the pegs on the toilet's overflow tube. Swing the flapper valve up and down to make sure it is properly seated on the pegs and will not fall off.
Twist the handle's chain to remove any kinks. Attach the toilet handle chain's hook to the loop on the top of the new flapper valve, then press the handle and release it several times to make sure the flapper valve swings up and down properly.
Turn the shutoff handle counterclockwise to refill the toilet's tank. Flush the toilet and check for any trickling after the flush has completed.