Toilets are not difficult to fix, because there aren't many parts that can go bad. Inside the tank is a float mechanism attached to a water intake valve for filling the tank with water. A flapper allows the water to flow into the toilet bowl when you flush the toilet handle. There's also an overflow tube that allows water to flow into the bowl even when the flapper is closed, so water won't overflow onto the floor if it rises too high. If all of these parts are old and starting to fail, you might want to replace them all at once.
Things You'll Need
Universal toilet repair kit
Toilet flush handle lever
Remove the Valve and Float Mechanism
Turn the valve that shuts off the water clockwise. This valve is on the wall or on the floor underneath the tank. Flush the toilet to empty the tank. Remove any additional water from the tank with a sponge.
Unscrew the water supply hose from the bottom of the tank with your fingers or with pliers. Catch any drips with a sponge.
Remove the larger nut just above the water supply hose that you just removed; this nut secures the water intake valve to the bottom of the tank. Reach inside the tank and lift out the water intake valve and the float attached to it.
Remove the Flush Handle, Mounting Screws, Overflow Tube, and Flapper
Unscrew the plastic nut on the inside of the flush handle, using pliers. Unhook the chain that connects the flush handle to the flapper. Slide the flush handle forward, out of the hole in the tank.
Remove the two nuts beneath the toilet tank, located to the left and right of the tank center, using an adjustable wrench. Lift the tank off the base and set it on the floor. Remove the two mounting screws at the base of the tank, and their accompanying washers.
Turn the tank over and remove the jam nut from the bottom of the tank (this is the large nut in the center, at the base of the overflow tube), using channel-lock pliers. Reach inside the tank and remove the overflow tube.
Replace the Overflow Tube, Flapper, Mounting Screws, and Flush Handle
Place a new toilet overflow tube into the hole in the bottom of the tank (new overflow tubes include a new flapper.) Align the flapper inside the tank similar to how the old flapper was aligned. Screw the jam nut and washer onto the bottom of the tank, tightening with channel-lock pliers.
Insert new toilet mounting bolts into the two holes in the bottom of the tank, with rubber washers as explained in the accompanying instructions. Place the toilet tank on the base with the screws going down through the holes in the toilet base. Tighten two nuts with washers onto the bottom of the mounting screws with pliers.
Slide a new flush handle into the hole in the tank, the same way the old one came out. Slide the mounting nut onto the inside of the flush handle, and tighten with pliers. Attach the chain on the handle to the flapper.
Replace the Valve and Float Mechanism
Reach inside the tank and insert a new water intake valve into the hole in the bottom of the tank. Tighten the mounting screw on it from the bottom of the tank with pliers.
Place the small rubber tube attached near the top of the water intake valve inside the overflow tube.
Screw the water intake hose to the bottom of the intake valve under the tank as tight as you can with your fingers. Turn on the water supply valve. Replace the toilet tank cover.
Do not overtighten the toilet mounting bolts or you could crack the porcelain tank.
Universal toilet repair kits include the water valve, overflow tube, flapper, and mounting bolts.