How to Replace a Toilet Flapper (and Stop a Running Toilet)

First, make sure the flapper is the likely problem

Take the tank lid off and set it somewhere safe. If the toilet has not been flushed recently but you can see a thin ripple of water moving into the bowl, the flapper may not be sealing. You may also hear the fill valve switch on for a few seconds at a time even though nobody has used the toilet.

For a simple check, put a few drops of food coloring in the tank and wait about 15 minutes without flushing. If colored water appears in the bowl, water is passing from the tank. The flapper is a common culprit, although a damaged flush-valve seat or an incorrectly set water level can cause similar symptoms.

What you will need

You should not need sealant, glue, or plumber's tape for a standard flapper replacement. The part is designed to attach to the flush valve and seal on its own.

• A compatible replacement flapper
• A sponge or small towel
• Rubber gloves, if you prefer them
• Food coloring for an optional leak test

Replace the flapper in six steps

1. 1

   Close the toilet's shutoff valve

   Turn the small valve at the wall or floor clockwise until it stops gently. Do not force a valve that is stuck or badly corroded. Flush once and hold the handle down so most of the tank water drains into the bowl.

2. 2

   Remove the old flapper

   Unhook the flapper chain from the flush lever. Slip the flapper's rubber ears off the two mounting pegs, or remove its ring from the overflow tube, depending on the design. A sponge can pick up the small amount of water left in the tank.

3. 3

   Wipe the sealing surface

   Run a clean cloth around the rim where the flapper sits. A small bit of grit or mineral residue can keep a new flapper from sealing. The rim should feel smooth and solid, not chipped or badly pitted.

4. 4

   Install the new flapper

   Attach it to the same pegs or overflow tube used by the old one. Make sure it sits flat over the opening and moves freely without rubbing against the tank wall or fill-valve parts.

5. 5

   Connect and adjust the chain

   Hook the chain to the flush lever with a little slack remaining when the flapper is closed. About half an inch of relaxed movement is a useful starting point. A tight chain can hold the flapper open; too much slack can keep it from lifting fully or become trapped beneath it.

6. 6

   Turn the water on and test

   Open the shutoff valve slowly, let the tank fill, and flush several times. The flapper should lift cleanly, stay open long enough for a complete flush, and then settle evenly over the opening. Listen for the fill valve to stop and stay off.

Small adjustments that solve most follow-up problems

If the handle feels tight or the toilet keeps running, add one link of slack to the chain. If the handle moves a long way before the toilet flushes, shorten the chain one link. Keep the loose end trimmed or secured so it cannot slide under the flapper.

Some adjustable flappers have a float or dial that controls how long they remain open. Match the original setting first, then make one small change at a time. A toilet that flushes well should clear the bowl without holding the handle down and should refill once, not cycle repeatedly.

When a new flapper does not stop the leak

The flapper can be new and still not seal if the flush-valve rim is cracked, rough, or out of shape. The problem can also be higher in the tank: a fill valve that is set too high may send water continuously into the overflow tube. Watch the water level after the tank fills. It should stop below the top of that tube.

Call a plumber if the shutoff valve will not close, water is leaking onto the floor, tank hardware is heavily corroded, the porcelain is cracked, or the toilet continues running after the flapper and chain are set correctly. Those signs point beyond the simple part you started with.