How to Repair a Fluidmaster Toilet Fill Valve

Fluidmaster toilet fill valve being replaced inside toilet tank

The Spruce / Kevin Norris

Project Overview
  • Total Time: 1 hr
  • Skill Level: Beginner

If you hear odd noises when you flush your toilet, it runs constantly, or it takes a couple of times to clear out the bowl, you may need to fix the toilet fill valve. This valve controls the refill of water in your tank after you flush. Fixing a toilet fill valve (once referred to as a ballcock) is relatively easy to repair if you have a standard Fluidmaster brand valve.

Often, a fill valve is repaired by simply replacing the entire fill valve, but Fluidmaster fill valves can be corrected by just replacing a seal inside the unit. If your Fluidmaster fill valve is not shutting off all the way or not filling quickly like it did when it was new, then replacing or cleaning the fill valve seal will most likely fix the problem.


Replacement seals for Fluidmaster fill valves are widely available at home centers and hardware stores. You should have no trouble finding one. And while you're at it, pick up an extra for the next time you have a problem. They are inexpensive.

How to Test Your Toilet Fill Valve

When your toilet is constantly running, the culprit is usually one of three things—the toilet fill valve, the float, or the flapper. The best way to tell if your fill valve is the problem is to remove the lid from your tank and observe what's going on as you flush the toilet. Do you notice a leak coming from any part of the fill valve? If not, lift the arm attached to the float as the tank fills up. When you lift the arm, the water should stop. If the water does not stop, there is likely something wrong with your fill valve, and a leak is happening inside the fill valve.

How Often to Replace a Fluidmaster Toilet Fill Valve

The manufacturer recommends replacing the entire valve or parts every five years to avoid flooding that could damage your home. If there's rust above the water line or rust or discoloration on the top cap lever arm assembly attached to the adjustment rod, it's strongly suggested that you replace the entire fill valve.

How to Repair a Fluidmaster Toilet Fill Valve

What You'll Need

Equipment / Tools

  • Mug or cup
  • Protective rubber gloves (optional)


  • Fluidmaster valve replacement seal


Materials and tools to repair a fluidmaster toilet fill valve

The Spruce / Kevin Norris

  1. Find the Shutoff Valve

    Locate the shutoff valve that controls the water supply to the toilet. The shutoff valve is usually located on the wall below the toilet tank and has a small handle. The valve will be connected to a water supply tube leading to the bottom of the toilet tank.

    Shutoff valve pointed out underneath toilet

    The Spruce / Kevin Norris

  2. Turn off the Water

    Shut off the water to the toilet by turning the handle on the shutoff valve clockwise until it stops.

    Water shut off by turning the shutoff valve under the toilet

    The Spruce / Kevin Norris

  3. Flush

    Flush the toilet to remove most of the water in the tank.

    Toilet being flushed with tank cover removed showing water and mechanics inside

    The Spruce / Kevin Norris

  4. Take off the Plastic Cap

    Loosen the plastic cap on the top of the fill valve: Wrap one hand around the fill valve shaft, then slide it up to push the float cup (the large plastic cylinder that slides on the valve shaft) up towards the top of the fill valve, and grasp the shaft firmly.

    Use your other hand to turn the cap on top of the fill valve counterclockwise 1/8 of a turn. It may help to push down on the cap while turning.

    Lift the cap from the top of the valve and set it aside. The valve seal is inside the cap.

    Plastic cap on fill valve taken off while holding the fill valve shaft

    The Spruce / Kevin Norris

  5. Position a Mug

    Place a mug or drinking cup upside down over the top of the valve and hold it in place with one hand.

    White mug positioned over top of fill valve in toilet tank

    The Spruce / Kevin Norris

  6. Flush the Shutoff Valve

    Use your other hand to carefully open the shutoff valve by turning it counterclockwise. Water will flow out of the fill valve, into the cup, and then down into the toilet tank. This flushes any debris from the valve.

    Toilet flush handle pushed down with water shooting out of fill valve into mug

    The Spruce / Kevin Norris

  7. Close the Valve

    Now close the shutoff valve by turning clockwise until it stops.

    Shutoff valve turned shutting of water

    The Spruce / Kevin Norris

  8. Take off the Old Seal

    Then remove the old fill valve seal from the valve cap.

    Old fill valve seal removed from valve cap in toilet tank

    The Spruce / Kevin Norris

  9. Position the New Seal

    Install the new valve seal, fitting the nipple on the seal over the stainless steel needle in the cap so the nipple goes up into the cap; this should match the orientation of the old seal.

    New valve seal inserted into stainless steel needle of cap

    The Spruce / Kevin Norris

  10. Put on the Fill Valve Cap

    Reinstall the fill valve cap by fitting it onto the valve as before and turning 1/8 turn clockwise to lock the cap in place.

    Fill valve cap reinstalled on the valve

    The Spruce / Kevin Norris

  11. Turn on the Shutoff Valve

    Open the shutoff valve slowly turning counterclockwise until the handle stops.

    Shutoff valve handle turned clockwise

    The Spruce / Kevin Norris

  12. Refill the Tank

    To finish the job, let the valve refill the toilet tank, then flush the toilet, and check the operation of the fill valve. Also, check for any leaks at the shutoff valve.

    Toilet tank refilled with water with handle pushed down to check fill valve

    The Spruce / Kevin Norris

Cleaning Tips for a Fluidmaster Toilet Fill Valve

  • Clean the valve of calcium or mineral build-up by dissolving it with vinegar applied with an old toothbrush. After the surface is clean, wash the valve with warm soapy water, then rinse.
  • Once a year, or if the fill valve will not turn off, remove the cap assembly and inspect the valve for debris. Place an inverted cup over the uncapped valve body and turn the water on for a few seconds to rinse out the valve. Remove and clean the seal and the cap. Then reinstall parts in the tank.
  • If you use bleach tablets to clean your bowl, inspect your tank more frequently. The bleach tablets may erode your toilet fill valve and seal.
  • How often will a Fluidmaster toilet fill valve need replacement?

    Fluidmaster recommends changing the fill valve or its parts every five years.

  • How difficult is it to change a Fluidmaster fill valve on a toilet?

    It's easy to change the toilet fill valve and takes about 30 minutes. The steps are straightforward, and the part is usually easy to find at any hardware store.

  • Is it expensive to change a Fluidmaster fill valve?

    If you're doing the work, it can cost about $10 to $60, depending on the Fluidmaster part and model you need. If a plumber does it, you can expect to pay about $60 to $400 for the parts and labor.