How to Replace a Toilet Flapper: The $4 Fix Most Plumbers Charge $120 For
How to Replace a Toilet Flapper: The $4 Fix Most Plumbers Charge $120 For
By Ariel, last updated July 1, 2026.
A toilet flapper is the rubber disc that lifts when you flush and re-seals the flush valve when the tank refills. It costs $4 at any hardware store and it is the most common cause of a running toilet and a climbing water bill. Replacing one takes eight minutes, no tools beyond a hand to reach into the tank. A plumber will charge you $120 to $180 to do it on a service call.
This guide walks the replacement step by step, but the two parts almost every other guide skips are the dye test (which confirms the flapper is actually the problem) and the sizing test (which confirms which flapper to buy before you stand in the Home Depot plumbing aisle).
How to replace a toilet flapper: the 5-minute version
The actual swap is the easy part. The longer this guide gets, the more you might think a flapper replacement is a complicated repair; it is not. Buy the right size, shut off the water, hook the new flapper on the same pegs the old one sat on, set the chain with a half-inch of slack. The detail below exists for the dye test, the sizing decision, and the four ways a new flapper can still leak after install.
The flapper fix in five steps
- Run the dye test first. If the dye does not migrate from the tank to the bowl, the flapper is not your problem.
- Measure the flush valve seat (2-inch or 3-inch) before you buy. Wrong size will not seal.
- Shut off the water, drain the tank, unhook the old flapper, hook the new one on the same pegs, set the chain with about half an inch of slack.
- Turn the water back on, let the tank fill, test flush.
- If the new flapper still leaks, see the four reasons in the troubleshooting section.
Total time: 8 minutes once the part is in hand.
Is the flapper actually your problem? The dye test
Take the tank lid off and drop one or two food-coloring drops (or a flapper-test dye tablet, $3 at the hardware store) into the tank water. Walk away for 10 minutes. Do not flush.
Come back and look in the bowl. If the bowl water has turned blue (or whatever color you used), the flapper is leaking water from the tank into the bowl. That is your problem.
If the bowl water is still clear after 10 minutes, the flapper is fine. The leak is somewhere else: the fill valve is overfilling and dribbling into the overflow tube, or the supply line is leaking, or you have a phantom flush from a different cause. Replacing a sealed flapper will not fix any of those.
This test takes 11 minutes and saves you a parts swap that does not solve the problem.
Which size do you need? 2-inch vs 3-inch
Toilet flush valves come in two common sizes: 2-inch and 3-inch. The number refers to the diameter of the opening at the bottom of the tank that the flapper seals.
2-inch is the older, more common size. Most toilets installed before 2005 use a 2-inch flush valve, and most basic two-piece toilets still do.
3-inch is what many high-efficiency 1.28 GPF toilets use. The larger opening drops more water faster, which is how a smaller flush volume still clears the bowl. TOTO Drake II, Kohler Cimarron Comfort Height, and anything labeled “wider flush valve.”
Note on the American Standard Champion 4: it does not take a 3-inch flapper. Per American Standard’s product documentation, the Champion 4 is “equipped with a large 4-in. flush valve (102 mm)” – the “4” in the name refers to that 4-inch flush valve, not a model number. Champion 4 replacements need American Standard’s proprietary 4-inch flush valve seal (kit 7301111-0070A), not a universal 2-inch or 3-inch flapper. Source: americanstandard-us.com Champion 4 product page.
How to tell without taking the toilet apart: look at the flapper currently in your tank. A 2-inch flapper is about the size of a coffee-cup saucer. A 3-inch flapper is about the size of a small dinner plate. If you cannot tell, take the old flapper out and lay it on a ruler. 2.05 to 2.15 inches diameter is a 2-inch flapper. 3.0 to 3.15 inches is a 3-inch flapper.
A universal flapper sold as “fits both 2-inch and 3-inch” exists. Skip it. The universal versions trade seal quality for fit range and they need replacing twice as often. Buy the size that matches.
Tools and parts
- One replacement flapper, sized to match your flush valve ($3 to $8)
- An old towel
- That is it. No wrench, no screwdriver, no plumber’s tape.
The two parts brands worth buying are Korky and Fluidmaster. Both are compared at the end. For now, grab either one in the correct size.
Step-by-step replacement
Step 1: Shut off the water
Reach behind the toilet to the chrome quarter-turn valve where the supply line enters the wall. Turn it clockwise until it stops. If your shutoff is the older oval-handle type, turn it clockwise as far as it will go.
If the shutoff valve will not turn, or it leaks when you try, stop. That is a different repair and the rest of this guide assumes a working shutoff.
Step 2: Drain the tank
Hold the flush lever down until the tank empties. Do not let go partway. A small amount of water will remain at the bottom of the tank; that is fine. Sponge or towel out what you can if the residual water bothers you.
Step 3: Unhook the chain
The thin metal or plastic chain runs from the flush lever arm down to the top of the flapper. Unclip it from the lever arm. Most chains have a small clip you squeeze.
Step 4: Unhook the flapper from the overflow tube
The flapper has two side ears that slide over two pegs on the sides of the overflow tube (the tall plastic tube in the middle of the tank). Slide each ear off its peg. The flapper lifts straight out.
Some older flappers are mounted with a circular ring around the base of the overflow tube instead of side ears. Slide the ring up and off the tube to remove that style.
Step 5: Inspect what you pulled out
Look at the old flapper. Warped rubber, mineral crust, or a curled sealing edge is your confirmation. If it looks fine, recheck the dye test.
One common surprise: in-tank chlorine tablets (the blue or white cleaners) destroy flappers from the underside up. The rubber looks fine on the seat side and rotten underneath. If your old flapper crumbles between your fingers, that is what happened. Stop using in-tank tablets.
Step 6: Install the new flapper
Slide the new flapper’s side ears onto the same pegs on the overflow tube. The flapper should hang flat over the flush valve seat with the chain side up. Press it down lightly. You should feel it seat onto the rubber ring at the bottom of the valve with no rocking.
Step 7: Set the chain length
Clip the chain to the flush lever arm. The chain should have about half an inch of slack when the flapper is closed and the lever is at rest.
- Too short: the chain holds the flapper open, water never stops running. This is the most common installation mistake.
- Too long: the chain pools below the flapper and gets caught underneath when the flapper drops, holding it slightly open. Phantom flush every 20 minutes.
- Correct: half-inch of slack, no kinks, chain runs straight down from the lever arm to the flapper.
Most replacement chains are too long out of the package. Pinch the chain a few links above where it attaches to the lever and use that link instead. The excess hangs free.
Turn the water back on and test
Open the shutoff valve counter-clockwise. The tank starts filling. Listen for the fill valve to shut off when the tank reaches the water line mark on the inside of the tank (or about 1 inch below the top of the overflow tube).
Press the flush lever. The flapper should lift cleanly and drop straight back onto the seat when the tank drains. The tank refills and the fill valve shuts off at the water line.
Wait 10 minutes. If you hear the fill valve cycle on by itself, you have a leak. See the next section.
Why your new flapper still leaks: four causes
1. Chain length is wrong
The single most common reason. Pull the lid back off, watch the flapper drop after a flush, and see if the chain pools under it. Re-adjust to the half-inch-slack rule.
2. Wrong flapper size
A 2-inch flapper on a 3-inch valve will sit inside the opening instead of sealing across it. Check what you bought against the seat diameter again. The Drake II is the most common toilet mis-flappered with a 2-inch part by mistake.
3. Flush valve seat is corroded
The rubber ring on the flush valve seat (the round opening the flapper closes against) degrades over years. Run a finger around it. If it feels rough or pitted, or shows mineral buildup, the new flapper is sealing against a damaged surface and will leak no matter what. Fix: a flush valve seat repair kit ($8 at the hardware store), which is a self-adhesive rubber ring you stick down over the old seat.
4. Flapper material does not match your water
Florida hard water and chlorinated municipal water eat rubber flappers fast. If your old flapper was crumbly after 18 months, switch to a chlorine-resistant flapper. Both Korky and Fluidmaster sell them, marketed as “chlorine-resistant” or “for chlorinated water.” Costs $2 more. Lasts 5x longer.
Best flappers, based on manufacturer specs and installer consensus
Three parts to know, sourced from Korky and Fluidmaster product documentation and installer forum consensus (Terry Love plumbing forum, PHCC):
Korky 2017 (2-inch, universal mount)
Korky’s flagship 2-inch flapper, marketed as the “2\” Ultra 2X Long Life High Performance Flapper” (retail pack SKU 2017BP). Red “Chlorazone II” chloramine-resistant rubber. Per Korky’s product page, engineered for 2X the life of a standard rubber flapper in chlorinated water. Retail pricing observed at Home Depot / Lowe’s as of July 2026: about $5 to $7. Source: korky.com 2017BP product page.
Fluidmaster 502 (2-inch)
Fluidmaster’s equivalent 2-inch. Red Microban-treated rubber. Same price band as the Korky 2017, slightly stiffer ears per installer forum reports. Pick whichever your local store stocks. Source: fluidmaster.com 502 product page.
Korky 3070 (3-inch, for Kohler and TOTO comfort-height)
Korky’s 3-inch chloramine-resistant flapper, marketed as the “Large 3\” 2X Long Life Universal Flapper” (retail pack SKU 3070BP; the non-2X sibling is the 3060). Fits the Kohler Class Five and TOTO Tornado flush valves per Korky’s compatibility list. Retail pricing observed at Home Depot / Lowe’s as of July 2026: about $8 to $10. If your toilet is a 1.28 GPF model from 2005 or later with a 3-inch flush valve, this is the one. Measure first. Source: korky.com 3070BP product page.
Skip any flapper that claims to fit both 2-inch and 3-inch valves. Installer forum consensus (Terry Love, PHCC) is that they leak earlier.
FAQ
How often should I replace my toilet flapper?
Every 4 to 6 years in average use, sooner if you have chlorinated water or run in-tank cleaning tablets (do not). When you start seeing dye-test failure or a phantom flush every 20 to 40 minutes, replace it.
Why does my new flapper still leak?
The four causes above, in order of likelihood: chain too short or too long, wrong size, corroded flush valve seat, or wrong rubber for your water. Run through them in that order.
Are universal flappers reliable?
No. The “fits 2-inch and 3-inch” universals trade seal quality for fit range, and they consistently leak earlier than size-matched flappers. The two minutes you save not measuring your seat will cost you a flapper swap in 18 months.
Can a bad flapper raise my water bill?
Substantially. Per EPA WaterSense, a worn flapper can silently leak thousands of gallons per year; household leaks total more than 9,300 gallons per year on average, and a running toilet can waste 50 gallons or more per day. Sources: epa.gov/watersense/fix-leak-week and epa.gov/watersense/statistics-and-facts. All of that for a $4 part you could have replaced in eight minutes.
Do I need to turn the water off?
Yes. The fill valve will start adding water as soon as the level drops below its trigger, and you cannot install a flapper into a tank that is constantly refilling.
Sources & references
- Korky 2017BP: 2″ Ultra 2X Long Life High Performance Flapper – Chlorazone II chloramine-resistant rubber spec
- Korky 3070BP: Large 3″ 2X Long Life Universal Flapper – 3-inch chloramine-resistant flapper spec and compatibility list
- Fluidmaster 502: 2″ Universal Toilet Flapper – Microban-treated rubber spec
- American Standard Champion 4 product page – verbatim: “Equipped with a large 4-in. flush valve (102 mm)”
- EPA WaterSense: Fix a Leak Week – flapper leak language and per-day loss
- EPA WaterSense: Statistics and Facts – household 9,300 gallons/year and nationwide 1 trillion gallons/year figures
- IAPMO: Uniform Plumbing Code 402 for fixture seal requirements
See also on My Best Toilet
- How to adjust a toilet float for when the flapper passes the dye test and the water level is the real problem
- How to fix a running toilet for the symptom-based flowchart when you are not sure which part has failed
- How to replace a toilet fill valve for the other half of the running-toilet diagnostic chain
- How to fix a wobbly toilet for movement at the base, which can also create false flapper symptoms
