How to Replace a Kohler Canister Flush Valve Seal

Last Updated on August 8, 2023 by toilethaven

If you own a modern Kohler toilet like the Kohler Cimarron, you know it uses a different flush valve from other toilets. Kohler toilets use an AquaPiston canister flush valve with a rubber seal/gasket at the bottom.

If you have a running Kohler toilet, it’s a sign that the canister flush valve seal is worn out, misaligned, or impeded by mineral deposits or debris.

In this case, water constantly flows from the tank to the bowl while the fill valve refills the tank. Apart from the irritating sound of a continually running toilet, your water bills will undoubtedly skyrocket.

Why Does Kohler Use a Canister Flush Valve?


Most people do not understand the technology behind the Kohler canister flush valve. “Why not just use the old ballcock and toilet flapper technology that has been time-tested and proven worthwhile”? They ask.

Here is the reason. An ordinary toilet flapper is hinged on one side. When you flush the toilet, the flapper lifts off to the hinged side. The cylindrical canister flush valve, on the other hand, lifts off vertically, allowing water to flow down the bowl from a 360 degrees angle (all sides)

This means water enters the bowl faster, creating more force and a powerful flush. The flush valve entry is wider than the exit by a ratio of 3:2. This means that the water exerts more pressure as it goes through the narrow section of the flush valve: the more pressure, the more powerful a toilet flushes.

More about the different flushing systems in this post.

How to Replace a Canister Flush Valve Seal

Replacing a Kohler canister flush valve seal is an inexpensive and quick repair you can comfortably do on your own. This repair wouldn’t take you more than 10 minutes.

Remember to use this genuine seal from Kohler. They last long and fit perfectly.

Step 1: Turn off the water to the toilet

  • The toilet shut-off valve is the knob on the wall behind the toilet. Turn the valve clockwise, and if you have a push/pull valve, pull it all the way out.
  • Flush the toilet and hold the handle down to remove as much water as possible.

Step 2: Remove the flush valve seal

  • Lift off the toilet tank lid and place it in a safe place. Remember, the lid is made of porcelain and could easily break.
  • Check the condition of the lift chain. The chain should not be too tight or too slack. If it is too tight, it will slightly unseat the flush valve seal causing a running toilet. If it is too slack, it will not fully lift the canister resulting in a weak flush/a toilet that does not flush fully. Ideally, there should only be 1 or 2 licks of slack when the toilet is not being used.
  • Disconnect the refill tube from the canister guide by simply pulling it out. The refill tube is connected to the fill valve. The refill tube sends some water down to the toilet bowl during a refill. This is the water you see at the bottom of the bowl. It acts as a barrier for sewer gases.
  • Lift the canister up and disconnect the lift chain.
  • Hold the canister guide and rotate it counterclockwise ¼ turn to remove it. Lift the whole assembly out.
  • Inspect the condition of the seal. Is torn/worn out? Is there dirt or mineral deposits on it and the flush valve opening?
  • Pull the seal out and remove it from the groove.
  • If the seal is dirty and the flush valve is in the same condition, clean both thoroughly until every iota of dirt is removed. Put the seal back on the canister and reinstall the canister. Turn on the water. Check for leaks.
  • If the toilet has stopped running, you may decide to save your new seal, but if you want a new one, just throw away the old one.
  • On the other hand, if the seal is worn out, go ahead and replace it.

Step 3: Install the new seal

  • Clean the canister groove and also the top of the flush valve opening.
  • Insert the new seal on the canister and run your finger around it to make sure it is fully inside the groove.
  • To install the canister, align the tab at the bottom of the guide with the flush valve slot. Rotate the guide clockwise ¼ turn to lock the canister in place.
  • Hook up the lift chain to the canister.
  • Attach the refill tube to the top of the guide.
  • Turn on the water to the toilet.
  • Confirm the toilet is not leaking.
  • Put the tank lid back on.

And that is simply how to replace a Kohler canister flush valve seal. To make sure that your toilet is not running at all, put some food color in the tank and wait for 30 minutes without flushing the toilet. If the food color appears on the bowl, you have a slow leak. If it doesn’t, you are home and dry.


1. How do I know my Kohler toilet model?

Lift the toilet tank lid and look at the wall opposite from you. The toilet model number will be stamped or molded using blue or black ink on the porcelain. If you need to replace a Kohler toilet or tank, use that number to order a new one.

2. How do you fix a Kohler toilet that keeps running?

A Kohler toilet that keeps running is mostly a result of a faulty canister flush valve seal. Replacing or cleaning the seal will fix the problem. Sometimes a running Kohler toilet could be due to a defective fill valve continuously feeding the tank.

3. Why is my Kohler toilet hissing?

If your Kohler toilet is making a hissing sound, especially after flushing, it likely has a defective fill valve. The fill valve opening could be blocked by mineral deposits, causing the water to force its way through it, resulting in a hissing sound. Replacing the fill valve could fix the problem.

4. How do you replace a Kohler canister toilet flapper?

A Kohler toilet flapper is a cylindrical canister that lifts up completely to allow water to flow through the bowl from a 360 degrees angle. To remove it, turn off the water to the toilet, rotate it a ¼, turn counterclockwise, and lift it off. To install a new one, align the guide to the base and rotate it ¼ turn clockwise.