How to Replace a Toilet Flush Valve Seal in Minutes!

Last Updated on October 4, 2023 by toilethaven

How Do You Change a Flush Valve Seal?

Toilet brands like Mansfield and some Kohler and American Standard models do not use the usual flapper flush valves. Instead, they use a canister or tower flush valve, which uses a flush valve seal instead of a flapper.

Unlike a toilet flapper hinged to one side, canister or tower flush valves lift off wholly when the toilet handle is pushed down. This allows water to flow from the tank down to the bowl from all sides and hence a powerful siphon and, as a result, a strong flush.

Due to water quality, age, and frequency of use, among other factors, the flush valve seal starts to warp or wear out, failing to create a watertight seal. This is what happens when you have a running toilet.

With a running toilet, when the water level in the tank falls below a certain point, the fill valve will open up, allowing the tank to refill on its own. This is the phenomenon mostly referred to as ghost flushing.

Apart from a running toilet, another sign that your flush valve seal is warped/worn out is when the toilet lever becomes very hard to pull due to the pressure exerted by the seal. If not fixed, the toilet trip can even break when pulled forcefully.

To replace a flush valve seal, turn off the water to your toilet, remove the tank lid, and flush the toilet. Disconnect the refill tube trip from the tower and lift it off. Pull out the old seal and put the new one nicely on the groove. Put back the tower, connect the trip, and refill the tube. Turn the water back on and test the new seal.

Whenever possible, I would advise using the toilet manufacturer’s original flush valve seal. Although you can get generic flush valve seals on the market, they are not as good as the original ones and will either leak or deteriorate quickly.

Since toilet tank designs are different, I will first show you how to replace the flush valve seal in a Mansfield toilet, then a Kohler toilet, and later an American Standard toilet.

I will also show you how to replace a flush valve seal in a dual flush toilet since they also use it.

How to Replace a Flush Valve Seal in a Mansfield Toilet

• Start by turning off the water to the toilet. The toilet shut-off valve is located on the wall behind the toilet. Turn it counterclockwise, but if it is a push/pull valve, you will need to pull it out.
• Flush the toilet and hold the trip lever down to remove as much water as possible.
• Lift off the toilet tank lid with both hands and place it away in a safe place where it cannot fall off and crack.
• Remove the refill tube from the top cap. The refill tube is the thin tube connected from the fill valve to the flush valve tower. You just need to pull it out of the stop cap.
• Unscrew the top cap. The top cap is threaded on the tower, so you only need to turn it counterclockwise.
• Disconnect the toilet trip from the flush valve tower. You will need to lift the tower slightly and bend it away from the trip to slide it out.
• Lift off the tower and place it away.
• You can now see the flush valve seal at the bottom of the tank. It is usually red in color.
• Pull the flush valve seal out of the groove.
• If the groove looks dirty, clean it using a soft rag.
• Insert the new flush valve seal, and most importantly, make sure that it is sitting pretty inside the groove. To do this, put only a small part of the seal in the groove first, then move around until the last piece, where you will need to pull it slightly.
• To confirm that the seal is properly seated in the grove, rotate it 360 degrees. If it moves freely, then it is properly seated.
• Take the flush valve tower and place it back, but connect the trip lever to it before pushing it all the way down.
• Screw in the top cap.
• Connect the refill tube to the stop cap.
• Turn the water to the toilet back on.
• Flush the toilet and check if the trip lever is moving free. You can even go ahead and test if the leak has stopped.

And basically, that is how to replace a flush valve seal in a Mansfield toilet.

How to Replace a Flush Valve Seal in a Kohler Toilet

• Turn off the water to the toilet.
• Flush the toilet and hold down the lever until all the water has exited the tank.
• Remove the tank lid and place away in a safe place.
• Pull out the refill tube from the top of the canister.
• Disconnect the trip lever lift chain from the canister. Mark exactly where the lift chain was connected to the canister to prevent it from being too tight or slack later when putting it back.
• Grab the top cap or body of the center support, turn it 1/8, turn counterclockwise, and lift off the entire canister assembly.
• You will see the flush valve seal at the bottom of the canister assembly.

• Pull out the old flush valve seal out of the groove.
• Use a soft cloth to clean the groove as well as the bottom of the toilet tank where the seal sits.
• Work the new flush valve seal along the groove of the canister until it is all in and can rotate freely.
• Put back the whole canister assembly at the bottom of the tank to engage the center support, then turn it 1/8 turn clockwise to lock it in position.
• Connect the refill tube back to the top of the cap.
• Attach the lift chain (where you marked it) to the canister.
• Turn on the water to the toilet and flush it severely. Test if the leak has stopped as well.
• Put back the tank lid.

How to Replace a Flush Valve Seal in an American Standard Toilet

If your American Standard toilet (like the Champion 4) uses an accelerator flush valve, it will start to leak once the flush valve seal is worn out. Here is how to replace it:

• Start by turning off the water to the toilet and holding the toilet handle down to remove as much water as possible.
• Remove the toilet tank lid and place it away.
• Detach the trip lever rod from the flush valve lift chain. You may need needle-nose pliers for this. Again, note where the chain was connected to avoid adjusting it later.
• Lift the flapper and unscrew the flush valve lift chain.
• The flapper is made of 2 halves, and the flush valve seal is installed in a groove in the upper half. Open the flapper and pull the seal out of the groove.
• Insert the new flush valve seal in the groove and close the flapper.
• Screw the flush valve lift chain and connect it back to the trip lever rod.
• Turn the water to the toilet back on and function test the new flush valve seal.
• Put the lid back on.

The video below from American Standard will show you all the steps involved:

And that is how to replace the flush valve seal in an American Standard toilet.

How to Replace a Flush Valve Seal in a Dual Flush Toilet

If you have a running/leaking dual flush toilet (flushed using buttons at the top of the lid), the flush valve seal is usually the problem. Replacing it will help fix the problem. This is a simple task.

• Turn off the water to the toilet.
• Flush the toilet by pressing down the big button.
• Lift off the tank lid and place it aside.
• Grab the flush valve assembly at the middle of the tank and give it 1/8 turn counterclockwise.
• You will see the flush valve seal at the bottom of the assembly.
• Pull the flush valve seal out and throw it away.
• Clean the groove as well as the bottom of the tank using a soft cloth.
• Insert the new flush valve seal around the groove of the assembly.
• Run your finger around the seal to make sure that it is sitting pretty inside the groove.
• Push back the flush valve assembly and give it a 1/8 turn clockwise to lock it in position.
• Turn the water to the toilet back on.
• Flush the toilet several times and test if the leak has stopped.

That is how to replace a flush valve seal of a dual flush toilet. I hope that this guide was of help to you.