Old rubber feels soft or sticky
Replace it. Soft, sticky rubber often cannot seal consistently even if it looks mostly intact.
Toilet Flapper Replacement
A bad flapper is the most common reason a toilet keeps running or refills by itself. Replacement is usually a 5 to 10 minute repair.
Flapper Replacement Examples
New flapper still leaks
Check chain slack, flapper size, and the valve seat surface before replacing another part.
Weak flush after replacement
The chain may be too loose or the adjustable flapper may be set to close too quickly.
When the Flapper Is the Likely Cause
- Pressing down on the flapper stops the running
- The toilet refills randomly even when nobody flushed
- The rubber looks warped, cracked, slimy, or covered in mineral buildup
- The flapper does not fall flat onto the valve seat
- The chain has slack, but the tank still leaks into the bowl
How to Replace It
- Turn off the toilet supply valve and flush to lower the tank water
- Unhook the chain from the flush lever
- Detach the old flapper ears from the overflow tube posts
- Take the old flapper to the store or match the toilet model online
- Attach the new flapper and leave about 1/2 inch of chain slack
- Turn water back on and test several flushes
Common Flapper Mistakes
- Buying a 2 inch flapper for a 3 inch flush valve
- Leaving the chain too tight so it holds the flapper open
- Leaving the chain too loose so the flush is weak
- Installing a universal flapper without adjusting its water-use setting
- Ignoring a rough or damaged valve seat
Common Questions
How do I know what toilet flapper to buy?
Match the flush valve size and, when possible, the toilet model. Many older toilets use 2 inch flappers; many newer high-flow valves use 3 inch flappers.
Do I need tools to replace a toilet flapper?
Usually no. Most flappers unhook by hand. Gloves and a towel are helpful, but the repair is normally tool-free.
Why does my new flapper still leak?
It may be the wrong size, the chain may be too tight, the valve seat may be dirty or rough, or the flapper may need its water-use setting adjusted.
Related Running Toilet Resources
Plan This Project in ChatDIY
Use ChatDIY to match your flapper symptoms to the correct replacement and chain adjustment.