Replacing a toilet flapper is a straightforward DIY repair that can stop continuous water waste and reduce utility bills. A worn or faulty flapper is the most common cause of a running toilet, often leaking hundreds of gallons per month. The process typically takes under 10 minutes and requires no specialized tools—just a replacement flapper (available for $5–$20) and basic household items like scissors.

Key steps from reliable sources include:

• Turning off the water supply and fully draining the tank by flushing ^[1][3][5]
• Disconnecting the lift chain and removing the old flapper by unclipping its side ears from the overflow tube pegs ^[4][3]
• Installing the new flapper by aligning its ears with the pegs and reconnecting the chain with ½ inch of slack ^[1][5]
• Testing for leaks by adding dye tablets to the tank or observing water flow after refilling ^[8]

Most tutorials emphasize checking the flapper’s seal against the valve seat and cleaning mineral deposits if leaks persist after replacement ^[9]. Older toilets may require disassembling the flush valve to access non-rubber flappers ^[7].

Step-by-Step Toilet Flapper Replacement Guide

Preparing the Toilet and Removing the Old Flapper

Before starting, gather a new flapper (universal models fit most toilets), heavy-duty scissors, and a towel. The Spruce notes this project costs $5–$20 and takes about 1 hour for beginners, though videos demonstrate it can be done in under 10 minutes with practice ^[4]. Begin by shutting off the water supply valve located behind or beneath the toilet—turn it clockwise until tight. This prevents flooding during the repair ^[1][3][5].

Next, flush the toilet to empty the tank completely. Hold the handle down to drain as much water as possible, then use a towel to soak up any remaining water at the tank bottom ^[3][8]. Remove the tank lid and set it aside on a soft surface to avoid cracking. Inside the tank, locate the flapper—a rubber or plastic seal at the base connected to a lift chain. Key components to identify:

• Flapper: The circular seal (usually red, black, or blue) covering the flush valve opening ^[4]
• Lift chain: Connects the flapper to the flush handle lever; should have slight slack when the flapper is closed ^[1]
• Overflow tube: The vertical pipe where the flapper’s side ears attach to pegs ^[4]
• Flush valve seat: The opening the flapper seals against; mineral buildup here can cause leaks ^[9]

Disconnect the lift chain from the flush handle lever by unhooking it, then detach the chain from the flapper’s tab ^[4]. Most flappers have two side ears that slide onto pegs on the overflow tube—pinch these ears inward to release them ^[4][3]. If the flapper is stuck due to mineral deposits, the City of Tacoma’s tutorial suggests gently twisting it while pulling upward ^[3]. For older toilets with metal or non-rubber flappers, Reddit users recommend disassembling the flush valve from the top to access the plunger mechanism ^[7].

Installing the New Flapper and Testing for Leaks

Select a replacement flapper that matches your toilet’s brand and flush valve size. Universal flappers like the Fluidmaster 502 or Korky 2000 series fit most models, but The Spruce advises checking the old flapper’s size (typically 2" or 3") before purchasing ^[4]. If your toilet has a deteriorated valve seat, consider a flapper with an integrated seal or a repair kit like the Fluidmaster 5403, as suggested in DIY Stack Exchange discussions ^[9].

To install the new flapper:

• Align the flapper’s side ears with the pegs on the overflow tube and press down until they snap into place ^[3][5].
• Reattach the lift chain to the flapper’s tab, leaving ½ inch of slack when the flapper is closed. Too much slack prevents a full seal; too little restricts the flush ^[1][8].
• If the chain has a metal clip, use pliers to adjust its length. For plastic chains, trim excess with heavy-duty scissors ^[4].

Turn the water supply back on and let the tank refill. Test the flapper by:

1. Adding a dye tablet (or food coloring) to the tank—if color appears in the bowl without flushing, the flapper isn’t sealing ^[8].
2. Listening for continuous water flow after the tank fills. A properly installed flapper should stay closed until the next flush ^[5].
3. Checking for "ghost flushing," where the toilet randomly refills due to a slow leak ^[4].

If leaks persist, clean the flush valve seat with a scouring pad or vinegar to remove mineral deposits, as recommended in multiple DIY forums ^[9]. For toilets with a threaded center screw (as mentioned on Reddit), ensure the new flapper’s gasket sits flat against the seat—uneven threading can prevent a tight seal ^[6].