How to Fix a Toilet That Will Not Fill Up

Find the supply valve for the toilet. Trace the water supply hose from the rear of the toilet to the valve located on the wall. This is the supply valve. Twist the supply valve's knob clockwise to turn off the toilet's water supply.

Pull the lid off the top of the toilet.

Push down on the toilet's handle and continue holding it down until all the water disappears from the toilet's tank under the lid.

Find the fill valve near the base of the toilet's tank. Look on the underside of this fill valve to find the water supply coupling, then unscrew it using a socket wrench.

Unscrew the toilet's retaining ring from within the valve using your fingers.

Pull out the entire fill valve assembly from the toilet now that it's been loosened. The attached rod should also be pulled out with the valve assembly.

Look on the bottom of your replacement fill valve to find the valve's gasket. Add silicone grease to the surface of this gasket, then turn the valve back around and reinsert it into the tank in the spot vacated by the old fill valve assembly.

Screw the toilet's water supply coupling and retaining ring back into place. Tighten the bottom of the valve assembly using pliers.

Turn the toilet's water valve knob counterclockwise to activate the water supply. Wait for the tank to fill back up and slide the lid back into place over it.