How to Replace a Toilet Flapper


A toilet flapper is a vital component of the flush valve assembly found in most modern toilets. Made of rubber or neoprene, the flapper acts as a seal to prevent water in the tank from flowing down into the bowl. Over time, toilet flappers can become cracked, misaligned, or simply wear out, resulting in leaks that cause the toilet to continuously run. Replacing a worn-out toilet flapper is an easy DIY project that can quickly fix toilet leaks and running water problems.

In this comprehensive guide, you’ll learn everything you need to know about how to replace a toilet flapper. We’ll cover the steps for identifying when you need a new flapper, choosing the correct replacement flapper, removing the old flapper, installing the new one, and adjusting it to stop the running toilet. With just a few tools and supplies, you can replace the flapper in less than 30 minutes. Let’s get started!

When to Replace a Toilet Flapper

Here are some signs that indicate it’s time to replace your toilet’s flapper:

  • Toilet Continuously Runs: If you can hear water constantly running in the toilet bowl, the flapper is likely leaking. This allows water to continuously flow from the tank into the bowl.
  • Weak or Slow Flush: An old, worn-out flapper may not seal properly during flushing. This prevents the tank from filling fully, resulting in a lower water volume and weaker flush power.
  • Visible Leaks or Cracks: Check the flapper seal for any visible cracks, tears, or defects. Any imperfections mean it’s time for a new one.
  • Flapper Doesn’t Close Completely: If the flapper doesn’t drop down fully into the flush valve drain hole, it’s not sealing and needs to be replaced.
  • Toilet Needs Multiple Flushes: Having to flush more than once to clear the bowl is a sign that the flapper isn’t sealing correctly and should be replaced.
  • Flapper Is Stiff, Brittle, or Misshapen: A degraded, inflexible, or warped flapper needs to be replaced to ensure a proper seal.

Replacing the flapper as soon as you notice these signs can prevent wasteful water loss and stop hard-to-find leaks inside the toilet tank.

Choosing the Correct Flapper

With so many flapper styles and designs, it’s crucial to choose the right replacement to match your existing toilet components. Here are some tips for selecting a compatible flapper:

  • Match the Original: The easiest way is to bring your old flapper to the hardware store and find an identical replacement flapper. Snap a photo of the flapper if you’ve already discarded it.
  • Measure the Opening: Use a ruler to measure the diameter of the opening at the bottom of the tank where the flapper seals. This will determine the size you need.
  • Check the Mounting: Note how the old flapper connects to the flushing mechanism inside the tank. Choose a new flapper with the same style clip, slide, or screw mount.
  • Material: Select a flapper made of durable rubber or neoprene, in the same material as your old one. Avoid rigid plastic flappers.
  • Read Reviews: Consult customer reviews to confirm a particular replacement flapper correctly fits your specific toilet make and model.

Matching the correct replacement flapper style will ensure an easy, trouble-free installation.

How to Remove the Old Flapper

Replacing the toilet flapper starts with removing the old one. Follow these steps:

Shut Off the Toilet’s Water Supply

  • Locate the water supply valve behind or around the toilet bowl.
  • Turn the valve clockwise to shut off the water completely.

Flush the Toilet to Drain the Tank

  • Flush the toilet as usual to empty all water out of the tank.
  • Sponge up any remaining water in the tank bottom with a towel.

Disconnect the Flapper Mount

  • Grasp the flapper where it connects to the flush valve or lift chain.
  • Disconnect it from the mount by unclipping, unscrewing, or sliding it off.

Remove the Old Flapper

  • For ringed flappers, stretch the ring to slide it off the valve.
  • Peel the entire flapper away from the tank bottom.
  • Discard the old flapper – avoid reuse.

With the tank drained and the old flapper removed, you’re ready to install the new replacement.

Installing the New Flapper

Follow these tips for properly installing a new replacement toilet flapper:

Prep the Flush Valve Seat

  • Examine the flush valve seat (black gasket) at the tank bottom.
  • Remove any debris buildup with steel wool or a scrub brush.

Position the New Flapper

  • Turn the water supply back on to refill the tank halfway.
  • Set the new flapper in place over the flush valve seat.

Attach the Flapper

  • For slide-mount flappers, align the slots and slide onto flush valve.
  • For ringed flappers, stretch the ring over the valve opening.
  • Clip or screw flappers affix as directed.

Connect the Chain

  • Attach the flapper chain to the arm on the flushing lever.
  • Ensure just enough slack for the flapper to seal completely.

Perform a Test Flush

  • Press the flush lever and allow the tank to refill.
  • Ensure flapper drops fully into the valve seat and rises back up into place to seal the tank.

The new flapper is now installed! Adjust as needed to ensure a complete seal.

Adjusting the Flapper

Sometimes minor adjustments are needed to get the new flapper sealing properly:

  • Add Weights: Clipping a coin or washer onto the flapper chain can help it drop more decisively into place.
  • Adjust Chain Slack: Eliminate excess chain slack so the flapper falls flat into the valve seat.
  • Check Seal Alignment: Press down around the edges of the flapper to check for complete contact with the flush valve seat.
  • Clean Valve Seat: Wipe the flush valve with steel wool to remove any dirt, buildup, or imperfections.
  • Shim Under Flapper: For a tight seal, place plastic shims or a ring of wax under the flapper to better match the angle of the valve seat.
  • Replace Tank Components: Misaligned pipes, a faulty valve seat, or incorrect flapper style may require replacing internal tank parts for a complete fix.

With the right adjustments, your newly replaced flapper will seal completely and stop that running toilet!

How to Replace a Toilet Flapper FAQ

Still have questions about replacing your toilet flapper? Here are answers to some frequently asked questions:

What are toilet flappers made of?

Most modern toilet flappers are made from rubber or flexible neoprene plastic. Avoid flappers made from stiff PVC, vinyl, or plastic.

Where can I buy replacement flappers?

Hardware stores, home improvement centers, and plumbing supply stores sell replacement flappers. Bring your old flapper to find an identical match.

Do all toilet flappers fit all toilets?

No, flapper sizes and attachment styles vary. Always match the replacement to your existing toilet make and model for proper fit.

How do I know if I need a 2″ or 3″ flapper?

Measure the diameter of the opening at the bottom of your toilet tank that the flapper covers. 2” or 3” refers to the circular opening size.

How can I fix a running toilet without replacing the flapper?

You can try adjusting the flapper chain for a tighter seal. Cleaning the flush valve seat may also help. But if worn out, replacement is required.

How long should a replacement flapper last?

Approximately 5 years is average but depends on frequency of use and water quality. Check regularly and replace again once signs of wear appear.

Can I just glue a cracked flapper instead of replacing it?

No, gluing or repairing an old, cracked flapper usually results in leaks recurring. It’s best to replace the entire flapper for a watertight seal.

Why does my new flapper keep leaking?

Double check the size matches the toilet valve seat diameter. Adjust the flapper chain length so it fully drops into place. Check alignment or shim under uneven spots.

How do I stop my toilet from running constantly?

A continuously running toilet is nearly always caused by a leaking, poorly sealing toilet flapper. Replacing the flapper will stop the running water.

Replacing a worn-out, leaking toilet flapper is an easy fix almost anyone can do to stop wasting water and eliminate phantom leaks. With the right tools and proper flapper selection, you can do the job in under 30 minutes. Just match the size and style, remove the old flapper, install the new one, and make any needed fit adjustments. Knowing how to replace a toilet flapper yourself allows you to quickly solve leaks and running toilet problems as soon as they occur.


Replacing a faulty toilet flapper is one of the handiest DIY repairs you can do to save water and stop leaks inside your toilet tank. Learning when flappers need replacement, choosing the right part, proper removal and installation, and adjusting for a leak-free seal are crucial steps covered in this guide. With the right know-how, you can now confidently handle this common toilet repair task and keep your flapper working properly for years before needing to replace it again.