A $10 flapper can be the most expensive part in an apartment. When it stops sealing, water slips from the tank into the bowl around the clock. Tenants rarely notice, and a running toilet can waste more than 200 gallons a day, according to EPA. EPA also names worn toilet flappers as one of the most common household leaks, which together can waste nearly 10,000 gallons a year per home.
This 2027 roundup covers flappers that hold up in rentals, how to pick the right size, and how often to replace them. Every product fact comes from the manufacturer's page, linked below.
What makes a flapper not leak
- Chlorine-resistant material. Municipal water is chlorinated, and chlorine breaks down standard rubber over time. Look for flappers marketed as chlorine resistant, like Korky's red rubber or Fluidmaster's chlorine- and hard-water-resistant 502.
- A frame that seats squarely. Fluidmaster says the solid frame on its 502 prevents twisting for a better seal.
- Adjustable vs. fixed. Adjustable flappers have a dial or float that sets how long the flapper stays open. That lets you match the toilet's rated flush volume (1.28, 1.6 gpf, etc.) instead of over-flushing. Fixed flappers are simpler but can't be tuned.
- Correct chain length. Fluidmaster recommends about 1/2" of slack. Korky warns that the wrong amount of chain slack can cause a weak flush or a slow leak beneath the flapper.
2" vs. 3" flappers: how to tell which you need
Measure the drain opening the flapper covers. Fluidmaster says a drain hole of about 2.5" takes a 2" flapper, and about 3.5" takes a 3" flapper. Korky notes that 3" flush valves are found in many newer 1.6 and 1.28 gpf toilets made since 2005. Some toilets, including certain American Standard and Kohler models, use proprietary seals or canister valves that universal flappers don't fit. Check the tank model number before you buy in bulk.
Best toilet flapper valves of 2027
1. AquaMizer FL-2 flapper with AM-2 fill valve (system retrofit): best for stopping flapper leaks at the source
Unlike the standalone flappers below, AquaMizer's FL-2 flapper comes as part of the AquaMizer Flush System, together with the AM-2 fill valve. AquaMizer's site doesn't list the FL-2 as a separate retail part or give a flapper size. The weighted flat flapper can be adjusted to set gallons per flush, and AquaMizer says it uses up to 52% less water per flush. UL Solutions verified the "up to 52%" flush-volume reduction claim for the AM-2 and FL-2. The AM-2 refills the tank only when someone flushes. If the flapper leaks, the tank empties instead of running all day, so no more than one tank of water is lost. Its encapsulated float also shuts off the water if a toilet clogs or the tank breaks.
Why it fits apartments: instead of swapping flappers after they fail, the system limits how much water a failed flapper can waste.
Rough cost: AquaMizer is sold and installed through AquaMizer distributors. For pricing, reach out for a quote on AquaMizer's How to Buy page.
Brand compatibility tip: when the original-manufacturer flapper is easy to get, it's the safest match. TOTO, for example, lists flush valve assemblies in its parts manuals. Use universal flappers when you need one part that fits many models across a portfolio.
2. Korky 100 Ultra High Performance (2"): best universal 2" flapper
Korky's 100 (also sold as 100BP) fits most 2" flush valves, including American Standard, Kohler, and TOTO, per Korky. It adjusts to 1.28, 1.6, 3.5, and 5 gpf tanks. Korky says its red rubber resists chlorine, bacteria, city water treatment, hard water, and well water. It is made in the USA, includes a stainless steel chain, and has a 5-year warranty. A 3-pack (100TP) is available for maintenance stock.
Rough cost: around $7 at Home Depot.
3. Fluidmaster 502 PerforMAX Adjustable (2"): best adjustable 2" flapper
The Fluidmaster 502P21 has a dial that sets water use per flush, a solid frame to stop twisting, and chlorine and hard-water resistance. Fluidmaster lists it for 1.28, 1.6, and 3.5+ gpf toilets with 2" flush valves and gives it a 5-year warranty. Fluidmaster's shop listed it at $7.99 when we checked. A 3-pack (502CN3) is also sold.
Rough cost: around $6.50 at Home Depot.
4. Korky 3060 Premium Universal (3"): best 3" flapper
Korky's 3060 is an adjustable 3" flapper. Korky lists fits for American Standard, Aquasource, Crane, Eljer, Ferguson, Gerber, Glacier Bay, Jacuzzi, Kohler, Mansfield, Pegasus, and TOTO 3" valves, including American Standard Cadet 3, Mansfield Maverick, and TOTO Drake (ST743). It uses the same chlorine-resistant red rubber and has a 5-year warranty.
Rough cost: about $11–$12 at Home Depot.
5. Fluidmaster 5403 Universal Adjustable (3"): best widely stocked 3" option
The Fluidmaster 5403 is a universal, adjustable 3" flapper for 3" flush valves. It is carried by large retailers such as The Home Depot, so it's easy to restock.
Rough cost: around $17 at Home Depot.
How to tell a flapper is leaking: the dye test
- Take off the tank lid and add a few drops of food coloring or a dye tablet to the tank water.
- Don't flush. Wait 10 minutes.
- If color shows up in the bowl, the flapper or flush valve seat is leaking. Flush afterward so the dye doesn't stain.
This is the method EPA describes in its Fix a Leak Week materials. Other signs include the tank refilling on its own (a "ghost flush"), hissing, or water constantly trickling into the bowl. If the flush valve seat itself is pitted, a repair kit such as the Korky 2" or 3" flush valve repair kits may be needed instead of just a flapper.
How often to replace flappers in rentals
No manufacturer gives one fixed interval. Warranties on the products above vary, and real life depends on water chemistry, chlorine levels, and use. A practical plan for apartments:
- Dye-test every toilet at move-in, move-out, and during routine unit inspections.
- Replace any flapper that fails the dye test, looks warped or slimy, or feels soft or crumbly.
- Stock one or two universal flappers per size so techs can fix a leak on the first visit.
- Avoid in-tank chlorine or bleach tablets. Korky's product literature warns that chlorine causes flappers to deteriorate.
Don't wait for the next inspection to find a running toilet
Dye tests only catch leaks on the day you test. Between inspections, a flapper can fail and run for weeks. NOWi's published results show how often this happens:
- Los Angeles: 72% of 47 buildings were leaking within the first week of monitoring.
- San Francisco: 11 of 24 buildings were leaking, and ROI came in under 2 months.
- Garden-style community: a 1,521 GPH leak was costing $24,092.64 a month.
The NOWi Meter Monitor mounts on your water meter and alerts you when flow never drops to zero, like the steady overnight flow of a leaking flapper, so you can send a tech before it shows up on the next bill.
See how the NOWi Meter Monitor works →
Related reading: our multifamily leak detection buyer's guide and how much water an average apartment uses.