How to Repair a Fluidmaster Toilet Fill Valve

Fluidmaster Fill Valve Repair


  • 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 is responsible for controlling 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 happen to have a common Fluidmaster brand valve.

Often, repairing a fill valve is done by simply replacing the entire fill valve, but Fluidmaster fill valves can be repaired 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 to have on hand the next time you have a problem. They are very inexpensive.

How Often to Replace a Fluidmaster Toilet Fill Valve

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

What You'll Need

Equipment / Tools

  • Mug or cup
  • Protective rubber gloves (optional)


  • Fluidmaster valve replacement seal


  1. Find the Shutoff Valve

    Locate the shutoff valve that controls the water supply to the toilet. The 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.

  2. Turn off the Water

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

  3. Flush

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

  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.

  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.

  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.

  7. Close the Valve

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

  8. Take off the Old Seal

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

  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.

  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.

  11. Turn on the Shutoff Valve

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

  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.

Tips for Cleaning 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.