How do I know what size flapper my toilet needs?

Look at the flush valve drain hole inside the tank. If the opening is about 2 inches across, you need a 2-inch flapper (most toilets made before about 2005). If the opening is closer to 3 inches across, you need a 3-inch flapper (most high-efficiency toilets made after 2005). Many flappers are sold as universal kits with both sizes included so you don't have to measure.

Why does my flapper keep failing every few months?

If you use chlorine tablets in the tank or bowl, the chlorine breaks down standard rubber flappers within a few months. Switch to a chlorine-resistant flapper (Korky and Fluidmaster both make versions labelled chlorine-resistant or Korky Plus). They cost a few dollars more but last years instead of months.

Should I replace just the flapper, or buy a full repair kit?

If only the flapper is leaking, replace just the flapper — it costs $5–$10 and takes five minutes. If multiple parts are old, leaking, or the toilet is more than 10 years old, a full repair kit ($20–$35) replaces the flapper, fill valve, and flush handle in one go. Full kits are usually better value than replacing parts one at a time.

Do adjustable flappers really save water?

Yes, modestly. An adjustable flapper lets you tune how long it stays open per flush, which controls how much water is released. On older non-low-flow toilets you can usually save 1–2 gallons per flush without affecting flushing performance, which adds up over a year. On modern low-flow toilets, the savings are much smaller and not worth the tuning hassle.

Is a flapper the same as a flush valve?

No. The flush valve is the larger fixed assembly the flapper sits on top of. The flapper is the rubber seal that lifts when you flush. A bad flapper is a $5–$10 replacement. A bad flush valve usually means draining the tank and unscrewing the entire assembly — bigger job, but the part still costs under $20. If you've replaced the flapper twice and the toilet still runs, the flush valve seat may be cracked or warped.

Best Toilet Flappers and Repair Kits (2026)

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A running toilet wastes 1–4 gallons of water per minute and is almost always caused by a worn flapper — the rubber seal at the bottom of the tank that lifts when you flush. Flappers degrade from chlorine, hard water, and just plain age. Replacing one is a five-minute job and the part costs less than a takeaway coffee.

Below: how to pick the right flapper for your toilet, what to look for in a quality replacement, and five reliable picks across different toilet types and price points.

How to Tell If the Flapper Is Your Problem

The classic signs of a failing flapper:

Phantom flushing — the toilet refills on its own every few minutes, even when no one has used it
Continuous trickling — water never stops flowing into the bowl after a flush
Tank water level rising and falling — you can hear the fill valve cycling
A flapper that looks black, gummy, warped, or has a crack when you lift the tank lid

A simple confirmation: drop a few drops of food colouring into the tank water and wait 15 minutes without flushing. If colour appears in the bowl, water is leaking past the flapper.

Full step-by-step diagnostic and repair walkthrough: How to fix a running toilet.

What to Look For in a Replacement Flapper

Three specs matter:

Size — 2-inch vs 3-inch. Look at the drain opening inside the tank. Most toilets built before ~2005 use a 2-inch flapper; most high-efficiency toilets built after ~2005 use a 3-inch. If you're not sure, buy a universal kit that includes both sizes.
Chlorine resistance. If you put chlorine tablets in the tank or bowl, standard rubber flappers will fail within 2–6 months. Chlorine-resistant flappers (often labelled "Korky Plus" or "chlorine-resistant rubber") cost a few dollars more and last 5+ years.
Adjustability. Some flappers have a sliding dial that controls how fast the flapper closes — letting you tune water-per-flush. Useful on older non-low-flow toilets where you want to save water without replacing the whole toilet.

Everything else (colour, branding, included tools) is marketing.

Quick Picks

| Use case | Pick | Approx. price | |----------|------|---------------| | Most toilets — universal, simple | Korky universal 2-inch flapper | $5–$8 | | Newer high-efficiency toilet | Korky 3-inch flapper for high-efficiency toilets | $7–$10 | | Toilet with chlorine tablets | Korky Plus chlorine-resistant flapper | $7–$12 | | Want to save water | Fluidmaster adjustable flapper | $6–$10 | | Multiple tank parts failing | Fluidmaster complete toilet repair kit | $20–$30 |

Detailed Picks

1. Korky Universal 2-Inch Flapper — Best Default Choice

A Korky 2001BP-style universal flapper fits the vast majority of toilets sold before about 2005, plus many built since. It hooks onto standard flush valve overflow tubes and the rubber is more durable than most generic alternatives sold at the same price.

Use it for: Standard 2-inch drain toilets — most homes built before 2005 and a large number after.

What it costs: $5–$8 for a single, often less in a multi-pack.

Why this one: Korky has been the default brand recommended by US plumbers for decades. The rubber compound holds up better than no-name flappers from the same shelf, and the universal mounting hooks fit nearly every flush valve design.

Skip if: Your flush valve drain opening is closer to 3 inches across — you need the 3-inch version below.

2. Korky 3-Inch Flapper — For Newer High-Efficiency Toilets

Most toilets built after 2005 — and almost all toilets advertised as "high-efficiency" or "1.28 gpf" — use a 3-inch flush valve, which needs a 3-inch flapper.

Use it for: Modern high-efficiency toilets, especially Kohler, American Standard, and Toto models from the last 15 years.

What it costs: $7–$10.

Why this one: The 3-inch design moves more water faster, which is what high-efficiency toilets are designed around. Putting a 2-inch flapper on a 3-inch valve will leak — the seal won't close fully.

How to confirm sizing before you buy: Take the lid off the tank and measure the inside of the flush valve drain hole. If it's between 2.5 and 3.5 inches, you need 3-inch. Under that, 2-inch.

3. Korky Plus Chlorine-Resistant Flapper — If You Use In-Tank Cleaners

If you drop chlorine tablets in the tank or bowl, regular rubber flappers fail within months. The chlorine reacts with the rubber, which goes soft, then warped, then leaky.

A Korky Plus chlorine-resistant flapper uses a different rubber compound that holds up to long-term chlorine exposure.

Use it for: Any toilet where chlorine tablets are in use.

What it costs: $7–$12.

Better alternative: Stop using in-tank chlorine tablets. Bowl-only tablets that hang from the rim are gentler on flappers, and a regular cleaning routine plus monthly bowl cleaner achieves the same result without the rubber damage. But if you want to keep using tablets, this is the flapper to buy.

4. Fluidmaster Adjustable Flapper — For Water Savings

A Fluidmaster 555-style adjustable flapper has a sliding dial that lets you control how long it stays open per flush. Closing it sooner means less water released per flush.

Use it for: Older toilets (3.5+ gallons per flush) where you want to reduce water bills without replacing the whole unit.

What it costs: $6–$10.

Real-world savings: On an old 3.5 gpf toilet, you can usually drop water-per-flush to ~2.5 gallons without flushing problems. For a household of 4 flushing 5 times per day each, that's roughly 7,300 gallons saved per year — meaningful on a metered water bill.

Skip if: Your toilet is already a modern 1.28 gpf model. There's not much water left to save and tuning may cause incomplete flushes.

5. Full Repair Kit — When Multiple Parts Are Failing

If your toilet has been making noise for years, parts are likely failing in sequence. Rather than fixing one thing only to have the next thing break, a complete toilet repair kit replaces all the moving parts inside the tank in one go.

What's typically in the kit: flapper, fill valve (the float assembly that refills the tank), refill tube, and sometimes the flush handle and lever arm.

Use it for: Toilets older than ~10 years, toilets that have had multiple part replacements already, or anyone doing a bathroom refresh and wanting "good as new" tank performance.

What it costs: $20–$35.

Why it's better value: Buying parts separately costs roughly the same in total but spreads the work over multiple weekends. A kit is one Saturday morning and you're done for years.

Common Mistakes to Avoid

Buying the wrong size flapper. The single most common error. Always measure or buy a universal pack that includes both 2-inch and 3-inch.

Forgetting to shut off the water supply first. Turn the small valve behind the toilet clockwise to close, then flush to empty the tank. Otherwise water sprays everywhere when you lift the old flapper.

Overtightening the chain. A common rookie mistake. The chain that connects the flapper to the flush handle should have ½ inch of slack when the flapper is closed. Too tight and the flapper won't seal; too loose and you have to hold the handle down to flush.

Not cleaning the flush valve seat. The rubber flapper seals against a circular plastic or porcelain seat. If that seat has mineral build-up or grime, even a brand new flapper will leak. Wipe it clean with a wet cloth before installing the new flapper.

Using a coloured flapper with chlorine. The dye in coloured (red, blue) flappers reacts with chlorine even faster than plain rubber. Stick with black flappers if you use any chlorine products.

A Note on How These Picks Were Chosen

We are not a plumbing supply company and we have not tested every flapper on the market. These picks are drawn from Amazon's top-rated options that meet the criteria above (correct size labelling, chlorine-resistant variants where claimed, established brand reputation). They're starting points — if you find an equivalent product from another reputable brand at a better price, the buying advice in the "What to Look For" section applies regardless of brand.

How to fix a running toilet — full step-by-step repair walkthrough
How much does a plumber charge to fix a clogged sink? — when DIY isn't worth it
Best home repair tools for beginners (starter kit) — what you need beyond a flapper
How to unclog a toilet without a plunger — when the problem isn't the flapper