Replacing a toilet flapper is a simple DIY fix for a running toilet. Turn off the water supply, flush to empty the tank, unhook the old flapper from the flush lever and posts, then attach the new flapper. Adjust the chain with minimal slack, turn the water back on, and test the flush.

Why Replace Your Flapper?

The toilet flapper is a rubber or plastic seal at the bottom of your toilet tank. Its job is to hold water in the tank until you flush. Over time, flappers can warp, crack, or degrade due to mineral buildup and harsh cleaners. A damaged flapper allows water to slowly leak from the tank into the bowl, causing the toilet to run intermittently or continuously. Replacing it solves this water-wasting problem.

What You’ll Need

Replacement flapper (universal or specific to your toilet model) ($8-15)
Sponge or small cup (to remove excess water) ($2-5)
Towel (for spills)

Tip: Take a photo of your old flapper before buying a new one, or bring the old one to the hardware store to ensure you get a compatible replacement.

Step 1: Turn Off the Water Supply

Locate the shut-off valve behind your toilet, usually near the floor. Turn it clockwise until the water flow completely stops. This prevents the tank from refilling during the repair.

Step 2: Flush the Toilet to Empty the Tank

Press the flush handle to empty the toilet tank. Hold the handle down until as much water as possible drains out. Use a sponge or small cup to remove any remaining water from the bottom of the tank, ensuring a dry working area.

Step 3: Disconnect the Old Flapper

Unclip the chain that connects the flush handle lever to the flapper. Then, gently unseat the flapper from the flush valve drain opening. Most flappers have two “ears” that slide onto posts on either side of the flush valve. Carefully slide them off.

Step 4: Prepare and Install the New Flapper

Ensure the new flapper is clean and flexible. Slide its “ears” onto the corresponding posts of the flush valve. Make sure the flapper sits flat and evenly over the drain opening to create a tight seal.

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Our Pick

Korky Ultra High Performance Flapper ($8) — This universal 2-inch flapper is made of specialized red rubber that resists chlorine and hard water, lasting much longer than standard black flappers.

Some flappers might have a ring that fits around the overflow tube – position this correctly if present.

Step 5: Attach the Flapper Chain

Reconnect the flapper chain to the flush handle lever. Adjust the chain’s length so there’s only about 1/2 to 1 inch of slack when the flapper is fully closed. Too much slack can prevent a full flush; too little can prevent a complete seal.

Step 6: Turn On Water and Test

Rotate the shut-off valve counter-clockwise to restore the water supply to the toilet tank. Let the tank refill completely. Flush the toilet several times to check that the flapper creates a good seal and the tank stops filling once the water level is reached. Listen for any running water.

When to Call a Pro

If replacing the flapper doesn’t stop your toilet from running, or if you notice other issues like leaks around the toilet base, slow tank filling, or a malfunctioning flush handle, you might have a more complex problem. These could indicate a faulty fill valve, a compromised wax ring, or other internal tank component failures. A professional plumber can diagnose and fix these issues efficiently.

FAQ

How do I know if my flapper is the problem? To confirm a leaking flapper, add a few drops of food coloring to your toilet tank (do not flush). Wait 15-20 minutes. If colored water appears in the toilet bowl, your flapper is leaking and needs to be replaced.

Are all flappers universal? No. While many flappers are designed to be universal, some toilets (especially older models or specific brands like Kohler or American Standard) may require a particular type or size of flapper. It’s best to check your toilet’s make and model or take your old flapper to the store for a match.

What causes flappers to wear out? Flappers wear out due to age, constant exposure to chlorine from toilet bowl cleaners (which can degrade rubber), and mineral buildup from hard water. The rubber or plastic material becomes stiff, brittle, or develops cracks, preventing a proper seal.

Can a flapper be repaired instead of replaced? Generally, no. Once a flapper is warped, cracked, or has lost its sealing ability, it needs to be replaced. Attempts to repair it are usually temporary and ineffective, making replacement the most reliable long-term solution.