A toilet flapper is a small rubber or silicone valve inside the tank that controls the release of water from the toilet tank to the bowl when you flush. When the flapper becomes worn, warped, or misaligned, water can leak continuously from the tank into the bowl, causing the toilet to run and waste water.
Replacing a toilet flapper is one of the simplest toilet repairs—it usually takes less than 15 minutes. Start by confirming the symptoms below, then follow the steps to install a new flapper correctly.
Quick Answer
If your toilet runs intermittently or continuously, a worn flapper is usually the cause. Replacing the flapper restores the seal between the tank and bowl and typically stops the running immediately.
Common Signs of a Bad Toilet Flapper
- Toilet runs continuously or cycles on and off
- Hissing or trickling sound from the tank
- Water movement visible in the bowl
- Tank slowly loses water after flushing
- You have to hold the handle down for a full flush
Likely Causes
Flappers fail over time due to:
- Rubber deterioration or warping
- Mineral buildup that prevents sealing
- Chain becomes kinked or misaligned
- Improper flapper size or type
- Chemical tank cleaners degrading rubber components
Tools & Materials
You may need:
- Replacement toilet flapper
- Rubber gloves
- Sponge or towel
- Small container or bucket
Bring the old flapper to the store to make sure you get a compatible replacement.
Avoid using in-tank cleaning tablets—they shorten flapper life.
Step-by-Step: How to Replace a Toilet Flapper
1. Shut Off the Water Supply
Turn the shutoff valve clockwise below the toilet tank to shut off the water.
Flush the toilet and hold the handle down to drain most of the tank water.
Remove the tank lid carefully and set it aside safely.
2. Disconnect the Old Flapper
Unhook the chain from the flush lever arm.
Detach the flapper’s mounting ears from the pegs on the overflow tube or slide the collar off, depending on the design.
Inspect the flush valve seat for debris or mineral buildup.
3. Clean the Flush Valve Seat
Wipe the valve seat with a cloth or sponge to remove residue that could prevent sealing.
A clean surface helps ensure a watertight seal.
4. Install the New Flapper
Attach the new flapper to the overflow tube so it pivots freely.
Confirm that it sits flat and centered over the flush valve opening.
5. Adjust the Chain Length
Reconnect the chain to the flush lever, leaving about 1/2 inch of slack.
- Too tight prevents sealing
- Too loose causes weak flushing
The flapper should lift fully and close smoothly.
6. Restore Water and Test
Turn the water supply valve on completely (counterclockwise) and allow the tank to refill.
Flush the toilet and watch the flapper closing. The tank should fill once and remain silent afterward.
If Problems Continue
If the toilet still runs after replacement, check:
- Chain alignment or tangling
- Water level set too high
- Damaged flush valve seat
- Worn fill valve
Additional component replacement may be required.
Preventing Future Flapper Failure
- Replace flappers every few years as preventive maintenance
- Avoid placing chemical cleaners inside the tank
- Periodically inspect the chain’s slack and connections
- Clean mineral deposits with white vinegar during routine maintenance
To Hire a Plumber…
If the repair turns out to be more complicated than expected, you can always find a plumber near you.
For hiring advice, see Trade Secrets for Hiring the Right Plumber.
Related Articles
If you’re not sure what’s causing the problem, see our
Toilet Repair and Troubleshooting Guide for a complete diagnostic overview.
Also see:
