How to Repair a Leaky Toilet Flush Valve

flush valve repair kit
  • Working Time: 20 mins
  • Skill Level: Intermediate
  • Estimated Cost: $10

One of the most common and most frustrating toilet tank problems is the running of water through the flush valve, down into the toilet bowl. As the water continually leaks, the tank water level keeps falling, causing the toilet fill valve to constantly run in a futile effort to fill it back up. It's a wasteful and annoying problem. The common solution is to replace the flapper that seals the flush valve opening, a job made much easier with a repair kit, such as the Model 555C kit from Fluidmaster. The kit includes not only a new flapper, but also drain seat insert and a sealant ring that fits over the existing flush valve opening. This kit allows you to create a new valve seat and install a new flapper without removing the toilet tank to replace the entire flush valve.

This particular kit is for standard gravity-flush toilets and will fit most toilet designs with 2-inch flush openings designed for 1.28- to 3.5-gallon flushes. If your toilet is outside those specifications, look for a different kit that matches your toilet.

What You'll Need

Equipment / Tools

  • Screwdriver (if needed)
  • Sponge
  • Scrub brush (if needed)


  • 555C Universal flush valve kit
  • Steel wool or fine sandpaper


  1. Turn Off the Water Supply

    The first step in the toilet repair is to turn off the water supply to the tank. This is done by closing the shut-off valve, usually located between the water supply pipe and the flexible supply stube that leads to the toilet's fill valve on the bottom left side of the tank. Turn the handle on the valve fully clockwise to shut off the water. If your toilet does not have a fixture shut-off valve, you will need to shut off the water supply at the main shutoff valve for the home.

    toilet water supply shut off valve
  2. Remove the Old Flapper or Tank Ball Assembly

    Once the water supply is turned off, flush the toilet to drain the tank of most of the water.

    Depending on the age of your toilet, the flush valve can have either a rubber flapper or a tank ball assembly that controls the flow of water down into the toilet bowl during a flush. Both of these are usually mounted with a bracket that clamps over the overflow tube.

    Remove the old flapper or tank ball along with any brackets, guide wires, or flush lever chain. There should be nothing left of the old assembly, only the exposed seat of the drain valve. Be careful not to drop anything into the drain valve opening, as it could clog the toilet.

  3. old flapper flush valve
  4. Remove Remaining Tank Water

    Once the tank is drained and the old flapper is removed, there will still be a small amount of water left in the very bottom of the tank. Soak up this water with a sponge until the tank is fully empty.

    drain water from toilet tank
  5. Clean the Valve Seat

    If the old drain valve seat is brass (many are), it needs to be clean and smooth before installing the kit. The easiest way is to use steel wool or fine sandpaper to scour the valve seat clean of any residual debris. A plastic or porcelain flush valve opening can be cleaned with a scrub brush.

    After scrubbing, wipe off the valve seat with a moistened soft cloth, then dry it fully with a towel.


    If you notice cracks in the valve seat, it is beyond repair and will need to be replaced.

    cleaning flush valve seat
  6. Install the Sealant Ring

    Peel the paper off one side of the sealant ring included in the repair kit, then carefully center it over the cleaned valve seat. Press lightly to set it in place. Do not press too hard.

    preparation for new flush valve
  7. Position the Flapper Assembly

    Before you remove the paper on the sealant ring, test-fit to find the best location for the flapper assembly. Try to position it at about a 45-degree angle to the front of the tank, so that the cone-shaped bottom of the flapper can tank can freely pivot and open fully when lifted by the chain. Usually, the proper positioning is for the lift chain to be as close as possible to the handle lever. The chain should pull straight up or be angled slightly back toward the hinge of the flapper assembly.

    Once you have the proper location, remove the paper from the top of the sealant ring. Place the flapper assembly over the sealant ring in the proper position and press down firmly to seat it onto the sealant ring.

    replacement flush valve

    The ridges under the flapper ball valve seat press into the sealant putty, creating a strong, watertight seal.

    flapper ball
  8. Attach the Lift Chain

    With the new valve assembly firmly seated in position, the next step is to attach the lift chain.

    Position the flapper so it is fully down in the flush valve opening, and make sure the toilet flush rod is down. Connect the chain attachment clip to the nearest hole in the flush rod, then clip the plastic chain onto the clip so that there is a small amount of slack. Unneeded chain links can be clipped off, but leave a few extra links hanging from the clip in case adjustments are needed.

    chain attached to flush valve
  9. Turn On the Water and Fill the Tank

    Turn on the water supply, let the tank fill up, then check the flush operation. If you need to adjust the chain length to achieve proper operation, do it now. When operating properly, the flapper will lift up and the fill cup will tilt back to fill with water when the flush handle is pressed.

    fill valve