How to Replace a Toilet Fill Valve

Replacement toilet fill valve held up above toilet

The Spruce / Kevin Norris

Project Overview
  • Working Time: 15 mins
  • Total Time: 15 mins
  • Skill Level: Beginner
  • Estimated Cost: $8

The fill valve is the device that controls the flow of fresh water into the tank of your toilet. It is usually mounted on the left side of the toilet tank, with a tailpiece that extends through the bottom of the tank, where it attaches to a supply tube that runs to a fixture shutoff valve. This part is sometimes known as a ballcock, so named after a design that was once the standard. 

The toilet fill valve opens and closes every time the toilet flushes. Over time, the valve simply wears out and must be replaced. If the existing fill valve is an older model with a float ball, now is your chance to replace it with a more modern and dependable fill valve with its own integrated float cup.

You might also consider using this opportunity to also replace the flush valve assembly. These parts also go bad eventually, and if you want to do a maintenance upgrade, you can buy a kit that includes both the fill valve and flush valve assemblies. Be aware, though, that if you go this route, it will require you to temporarily remove the entire tank. 

The project shown here involves replacing only the fill valve, a relatively easy job that can be done with the toilet tank in place. 

Before You Begin

Turn off the water to the toilet by turning the handle of the fixture shutoff valve clockwise until it stops turning. Normally, the fill valve is located on a water supply pipe coming out of the floor or wall near the bottom left side of the toilet tank, near where the water supply tube connects to the tailpiece on the fill valve. 

Flush the toilet to empty the tank, then remove the cover on the tank and use a sponge to mop up any remaining water in the bottom of the tank.

What You'll Need

Equipment / Tools

  • Sponge and bucket
  • 2 channel-type pliers
  • Scissors (as needed)


  • Toilet fill valve


Tools and materials to replace a toilet fill valve

The Spruce / Kevin Norris

  1. Remove the Toilet Fill Valve

    To remove the toilet fill valve, first disconnect the water supply tube attached to the bottom of the fill valve tailpiece, using channel-type pliers or an adjustable wrench.

    Next, loosen and remove the mounting nut that holds the bottom flange on the fill valve to the bottom surface of the tank. You may need to reach down into the tank from the top and grip the bottom of the fill valve with another set of pliers to keep it from rotating as you loosen the mounting nut. 

    Disconnecting water supply tube with wrench to remove toilet fill valve

    The Spruce / Kevin Norris

  2. Prepare the New Fill Valve

    Slide the rubber washer included with the kit onto the bottom flange on the fill valve tailpiece. This washer will provide an inner seal that prevents leaking around the base of the fill valve.

    Adjust the height of the fill valve, if necessary. Different valves have different methods of doing this, but with most, it's a simple matter of screwing the stem piece shorter or longer so the overall length of the fill valve will fit inside your toilet tank. Ideally, the top of the fill valve should be slightly taller than the top of the overflow tube but not so tall that it will prevent the tank lid from closing.

    Rubber wing slid onto bottom flange of fill valve tailpiece

    The Spruce / Kevin Norris

  3. Install the New Fill Valve

    Set the fill valve into the toilet tank, inserting the tailpiece through the opening in the bottom of the tank. Position the valve so the water outlet nipple is facing the overflow tube in the tank.

    Holding the fill valve with one hand, use the other hand to thread the mounting nut onto the tailpiece from below the toilet. Tighten the mounting nut so it is hand-tight. Use channel-type pliers to tighten the mounting nut slightly further. Make sure not to twist the body of the fill valve inside the tank.

    Reconnect the water supply tube to the fill valve. Once again, hand-tighten first and then use pliers to tighten a little more.

    New fill valve threaded on mounting nut unto tailpiece hole from below toilet

    The Spruce / Kevin Norris

  4. Connect and Make Adjustments to the Fill Valve

    Attach one end of the rubber fill tubing to the nipple on the top of the fill valve, then attach the plastic or metal adapter onto the other end of the tubing and clip it to the top of the overflow tube.


    You may need to cut the rubber tubing with scissors if it's too long. It should make a smooth bend (with no kinks) when connected to the overflow tube.

    Turn on the water supply valve all the way, and watch as the toilet tank refills with water. Adjust the water level to a height that is appropriate for your toilet, following the valve manufacturer's instructions. The tank should fill to a marked water line on the inner walls of the tank; the water level should be about one inch below the top of the overflow tube.

    Inspect the fittings on the bottom of the tailpiece and shutoff valve to make sure there are no leaks. You may need to tighten them slightly more if there is any seepage. 

    Rubber fill tubing connected onto top of fill valve in toilet tank

    The Spruce / Kevin Norris