Measure the old flapper from edge to edge. About 3" across means you need a 2-inch flapper; about 4" across means a 3-inch flapper.
How wide is the old flapper?
Lay a tape across the rubber flapper at its widest part.
How wide is the hole it covers?
Turn the water off and flush to empty the tank, then measure across the opening at the bottom.
You most likely have
2-inch flapper
The old flapper is about 3" across.
On the package: 2 in. flapper
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3-inch flapper
The old flapper is about 4" across.
On the package: 3 in. flapper
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A canister (tower) flush valve
It has no flapper. It takes a replacement seal.
On the package: Canister seal for your toilet’s model
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Start overYou most likely have
American Standard Champion 4 valve
A 4" opening takes a Champion 4 seal where other toilets use a flapper.
On the package: Champion 4 replacement seal
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The size on the package is the drain it fits, not the width of the flapper.
Two ways to measure
Measure the flapper if it’s still in one piece: lay a tape across its widest part. Measure the drain hole if the old flapper is gone or warped: turn off the water, flush, and measure across the opening the flapper sits on.
A quick check needs no tape: a hole about the size of a baseball or an orange takes a 2-inch flapper; a hole the size of a softball or a grapefruit takes a 3-inch.
A 4-inch reading is the width of a 3-inch flapper, not the hole. If the hole itself is 4" across, you likely have an American Standard Champion 4 valve, which needs its own seal (see below), not a 3-inch flapper.
Which is more likely?
Older toilets mostly use 2-inch flappers; many newer ones use 3-inch. The manufacturers put the change at different years. Korky puts it at 2000, with most older toilets needing a 2-inch, and Kohler at 2004. Fluidmaster says most toilets made after 2005 have a 3-inch. Measure rather than guess from the age.
Flush valve types, including toilets that use neither
Toilet flapper sizes
| Flush valve | What you see | Replacement |
|---|---|---|
| 2-inch | Flapper about 3" across over a hole about 2.5" | 2-inch flapper |
| 3-inch | Flapper about 4" across over a hole about 3.5" | 3-inch flapper |
| Kohler Class Five | A Kohler toilet with Class Five on the model | Kohler’s 3-1/4" flapper |
| American Standard Champion 4 | An opening about 4" across | Champion 4 seal |
| Canister (tower) | A tall cylinder in the middle of the tank, no flapper | The canister’s seal |
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- A canister takes a new seal; replace the seal, not the canister.
- A Champion 4 seal from Korky replaces American Standard part 7301111-0070A.
- If you can’t tell, find the toilet’s model number. Kohler prints it on the inside back wall of the tank, with service information on the underside of the lid on toilets made after 1990. Search the model number with “flapper”.
Also check when you buy
- Water use. Fluidmaster makes adjustable flappers for 1.28 and 1.6 gallon-per-flush toilets, and non-adjustable ones (2-inch only) for 3.5 gallon and larger toilets.
- How it mounts. Most flappers hook onto two pins on the overflow pipe. If yours has no pins, Fluidmaster’s flexible flappers include a ring that slips over the overflow pipe instead.
- Universal flappers such as the Korky Fit-All and Fluidmaster 523A are made to replace both 2-inch and 3-inch flappers.
After it’s in
Set the chain with a little slack: about 1/2" between the handle lever and the flapper. Too much slack gives a weak flush.