Toilet Flapper 2 Inch vs 3 Inch by Model: Kohler, American Standard, TOTO, Gerber, Glacier Bay and Mansfield, and Which Toilets Take a Seal Instead

Check the size before buying: Korky lists the Gerber Viper under both its 2-inch and its 3-inch fit lists, so the model name on the tank does not settle it.

Which flapper or seal fits your toilet?

Three flush valve types exist. A flapper is a hinged rubber disc on a 2-inch or 3-inch seat. A canister or tower valve is a cylinder that lifts straight up and seals on a flat ring: Kohler’s catalog says these toilets “do not use a flapper, but a seal”. The OEM column carries only numbers a maker’s own document prints.

Kohler’s catalog lists K-3496 Cimarron in both its canister index and its flapper index. The same model number was sold with both valves, so open the lid.

Kohler’s catalog also says the toilet number is imprinted on the inside back of the tank and, after 1990, service information on the underside of the lid. TOTO stamps its model number on the back or right inner tank wall, and an E suffix marks a 1.28 gpf tank that may take a different flapper, per plumbingsupply.com’s identification page; Korky’s TOTO pages exclude the E tanks for that reason.

Which toilets take a seal, not a flapper?

If you lift the lid and see a tall cylinder in the middle of the tank instead of a hinged disc on a chain, no flapper on this page fits. Kohler’s catalog: if the toilet is leaking into the bowl, “the seal needs to be replaced, not the canister”.

How do you measure the flush valve?

Fluidmaster publishes two ways to get the same answer. Use whichever part you can reach with the tank drained.

1. Shut the supply, flush, and unhook the old flapper from its chain and ears.
2. Measure the flapper end to end: 3 inches across means buy a 2-inch flapper, 4 inches across means buy a 3-inch flapper, per Fluidmaster’s sizing page.
3. Or measure the drain hole the flapper covers: 2.5 inches means a 2-inch flapper, 3.5 inches means a 3-inch flapper, per Fluidmaster’s 502 page.
4. A cylinder instead of a disc means a seal: go to the table above.
5. On a 3-inch Mansfield or Cato tank, Fluidmaster says its 5403 lacks the frame adapters its 513A-016 carries.

Kohler’s catalog says toilets made before 2004 most commonly have a 2-inch flapper. That is a tendency, not a rule: the measurement decides.

How often does a flapper need replacing?

None of the makers in the table prints a replacement interval. The trigger is the leak, and the running toilet dye test tells you whether the flapper or seal is the part that has failed before you buy either.

Frequently asked questions

Sources

1. Kohler, Toilet Service Parts catalog, March 2015 (PDF): flush valve identification by flapper size and canister type, with a model index (manufacturer or vendor document)
2. Kohler, Toilets Service Parts catalog, May 2011 (PDF): the same identification guide, with the flapper-shape wording for GP87449 and GP85160 (manufacturer or vendor document)
3. Kohler Assist, GP1059291 Canister Seal Replacement Kit for Single-Flush Toilets (video page) (manufacturer or vendor document)
4. American Standard, Toilets Replacement Part Service Guide 2023 (PDF): tank model to flush valve and flapper or seal part number (manufacturer or vendor document)
5. Fluidmaster, Determining Whether You Have a 2 or 3 inch Flush Valve and Flapper (manufacturer or vendor document)
6. Fluidmaster, 502 Universal 2 inch Flapper product page (drain hole measurement) (manufacturer or vendor document)
7. Fluidmaster, Universal 3 inch Toilet Flapper 513A-016 product page (brand list and Mansfield/Cato adapters) (manufacturer or vendor document)
8. Fluidmaster, 5403 Universal Adjustable 3 inch Flapper product page (manufacturer or vendor document)
9. Mansfield Plumbing, Summit Pro 1.28 model 382-377 specification sheet, Rev. 10/18 (PDF): tank trim and replacement parts (manufacturer or vendor document)
10. Korky, Large 3 inch Fits Kohler Class Five Toilet Flapper, part 3010 (manufacturer or vendor document)
11. Korky, 2 inch Fits Kohler Rialto Float Toilet Flapper, part 2010 (manufacturer or vendor document)
12. Korky, 2 inch Fits Kohler Hinge Toilet Flapper, part 2011 (manufacturer or vendor document)
13. Korky, Large 3 inch Fits American Standard Cadet Toilet Flapper, part 3040 (manufacturer or vendor document)
14. Korky, 2X Long-Life Fits American Standard Champion 4 and Eljer Flush Valve Seal, part 450 (manufacturer or vendor document)
15. Korky, Fits American Standard and Kohler 3 inch Toilet Flush Valve Seal Kit, part 435 (manufacturer or vendor document)
16. Korky, 2X Long-Life Fits Kohler Toilet Flush Valve Seal, part 451 (manufacturer or vendor document)
17. Korky, Fits Mansfield 210 and 211 Toilet Flush Valve Seal, part 427 (manufacturer or vendor document)
18. Korky, What Flush Valve Seal Do I Need (Champion 3, Champion 4, Kohler Class Five and Six, Mansfield 210 and 211, Glacier Bay dual flush) (manufacturer or vendor document)
19. Korky, Glacier Bay Toilet Replacement Parts (dual-flush seals 441, 444 and 440) (manufacturer or vendor document)
20. Korky, Large 3 inch Fits TOTO Red Toilet Flapper, part 2021 (manufacturer or vendor document)
21. Korky, Large 3 inch Fits TOTO Blue Toilet Flapper, part 2022 (manufacturer or vendor document)
22. Korky, Large 3 inch Genuine TOTO Toilet Flapper, part 2023 (OEM numbers THU138S to THU500S) (manufacturer or vendor document)
23. Korky, QuietFILL Platinum Fill Valve and Large 3 inch Flapper Kit, part 830MP (3-inch fit list by brand and model) (manufacturer or vendor document)
24. Korky, 2 inch Ultra High Performance Toilet Flapper 3 Pack, part 100TP (2-inch fit list by brand and model) (manufacturer or vendor document)
25. Korky, Large 3 inch Premium Universal Toilet Flapper, part 3060 (manufacturer or vendor document)
26. plumbingsupply.com, Toto Toilets: Identify Your Toilet and Find Repair Parts (where the TOTO model number is stamped) (manufacturer or vendor document)