A toilet flapper is the rubber seal that lets water flow from the tank into the bowl, then closes to refill

When a flapper wears out or warps, water leaks constantly from the tank into the bowl—you'll hear the toilet refilling on its own every few minutes, or notice the water level dropping without anyone flushing. Replacing it is a straightforward job that takes about 15 minutes and costs $5 to $15 for the part. You need only a screwdriver and the old flapper to match at the hardware store.

The flapper sits at the bottom of the tank, attached to a chain or rod that connects to the flush handle. When you push the handle, the chain lifts the flapper, water rushes down, and the flapper falls back to seal the opening. Over time—usually two to five years—the rubber hardens, cracks, or warps, and water seeps past the seal.

Key Takeaways

  • Turn off the water supply at the shutoff valve under the tank before you start, then flush to empty the tank.
  • The flapper is a rubber disc at the tank bottom; remove it by unclipping or unscrewing the mounting hardware, then unhook the chain.
  • Take the old flapper to the hardware store to match the size and style—most are universal, but some older tanks use specific models.
  • Install the new flapper by reversing the removal steps: hook the chain, clip or screw the mount, then turn the water back on and test.
  • If water still leaks after replacement, the fill valve or tank rim may be damaged and need professional repair.

Turn off the water and empty the tank

Locate the shutoff valve on the water line below the toilet tank—it's a small knob or lever on the pipe coming from the wall. Turn it clockwise (or flip the lever perpendicular to the pipe) until it stops. You should feel resistance; do not force it.

Flush the toilet once to empty the tank completely. If water remains in the tank after flushing, the shutoff valve may not be working—in that case, you can still work, but water will spill when you remove the flapper. Have a bucket and towels ready.

Remove the old flapper and chain

Lift the tank lid and set it on a towel somewhere safe—it's ceramic and breaks easily. Look at the bottom center of the tank. The flapper is a rubber disc, usually black or red, sitting over a hole. A chain or rod connects it upward to the flush handle lever.

Most flappers clip onto a shaft or post that sticks up from the tank bottom. Squeeze or unclip the flapper from both sides of the shaft and lift it straight up. Some older models screw on; if you see a bolt, use your screwdriver to unscrew it counterclockwise. Unhook the chain from the flapper arm—it usually clips on or loops through a hole.

Inspect the hole the flapper covered. It should be smooth and clean. If you see mineral buildup, corrosion, or rough edges, wipe it gently with a damp cloth. A damaged rim can prevent a new flapper from sealing; if the rim is cracked or pitted, the tank may need replacement.

Match and buy the correct replacement flapper

Take the old flapper to your hardware store or home center. Most modern flappers are universal and will fit any standard tank, but some older toilets use specific models. The staff can confirm whether your old flapper matches a universal replacement or if you need a particular brand.

Universal flappers cost $5 to $15 and come with a new chain or clip hardware. If your old chain is kinked or corroded, buy a flapper kit that includes a new chain—it's easier than reusing the old one. Check the package to confirm it includes the mounting hardware you need.

Install the new flapper

Position the new flapper over the hole at the tank bottom. The flapper should sit flat and centered. If it has a clip or shaft mount, slide it onto the post and press down until it clicks or seats firmly. If it screws on, align the bolt holes and hand-tighten the screw clockwise, then snug it with your screwdriver—do not overtighten, or you may crack the plastic.

Hook the chain to the flapper arm. The chain should have just enough slack that when you lift the flush handle all the way, the flapper rises fully and the chain is taut but not pulling. If the chain is too tight, the flapper won't seal; if it's too loose, the flapper won't open fully. Most chains have multiple links—clip it to the link that gives you about 1/2 inch of slack when the handle is at rest.

Turn the water back on and test

Turn the shutoff valve counterclockwise (or flip the lever parallel to the pipe) to restore water flow. The tank will refill. Listen for the fill valve to stop—it should take 30 seconds to 2 minutes. Once the tank is full, the water should stop running.

Flush the toilet and watch the flapper rise as the handle goes down. The bowl should empty completely, and the tank should refill without leaking. Place your hand over the overflow tube (the hollow pipe in the center of the tank) to feel whether water is flowing into it—if it is, the flapper is not sealing and may be installed incorrectly or damaged.

Wait 10 minutes with the tank full and listen. You should hear nothing. If you hear the fill valve running every few minutes, the flapper is not sealing. Check that it's seated flat and centered over the hole. If it still leaks, the tank rim may be damaged, and you may need a plumber to assess whether the tank can be repaired or must be replaced.

Common mistakes to avoid

Do not overtighten the mounting hardware. Plastic clips and screws can crack if forced, and a cracked mount will leak. Hand-tighten first, then snug gently with your screwdriver.

Do not reuse an old chain if it's kinked, corroded, or stiff. A chain that doesn't move freely will prevent the flapper from opening or closing fully. Buy a new one with the flapper kit.

Do not assume the flapper is the problem if water is running constantly. If the tank is full and you hear water flowing into the overflow tube, the fill valve (not the flapper) is faulty. If water is leaking from under the tank or from the base, the tank seal or bolts need attention. A flapper only stops water from leaking into the bowl.

Frequently Asked Questions

How do I know if my flapper is actually broken?

Turn off the water and listen. If the toilet refills on its own every few minutes, or if you see water trickling into the bowl when nobody has flushed, the flapper is leaking. You can also add food coloring to the tank—if it appears in the bowl within 30 minutes without flushing, water is seeping past the flapper.

Can I use any universal flapper, or do I need a specific brand?

Most universal flappers fit any standard toilet tank made in the last 20 years. Bring your old flapper to the store to confirm the size and mounting style. Some older or specialty toilets (like dual-flush models) need specific flappers, but the staff can tell you in seconds by comparing the parts.

What if water is still leaking after I install the new flapper?

Check that the flapper is seated flat and centered over the hole, and that the chain has the right amount of slack. If it's installed correctly and still leaks, the tank rim may be damaged or mineral-coated. Wipe the rim with white vinegar and a cloth, let it soak for 15 minutes, then wipe again. If it still leaks, the tank may need professional repair or replacement.

Do I need to turn off the water to replace a flapper?

Yes. Turning off the water prevents spills and lets you work without water running into the tank while you're installing the new flapper. It takes 10 seconds and makes the job much cleaner.

How long does a flapper usually last?

Most flappers last two to five years, depending on water hardness and how often the toilet is used. Hard water and frequent flushing wear them out faster. If you replace one and it fails again within a year, the tank rim may be damaged and causing premature wear.