How to Fix a Running Toilet: Replacing the Toilet Flapper

No need to call a plumber – this is a quick and easy DIY fix!

The parts inside a toilet tank are continually submerged under water, and will therefore degrade over time. If your toilet is intermittently or sporadically running (and not flowing into the overflow tube), then you need to replace the toilet flapper.

In this post, I will show you how to replace the toilet flapper. It’s a very quick and easy fix (only takes 5-10 minutes and no tools are needed!), and new flappers are pretty cheap (approximately $10). Definitely no need to call a plumber, so roll up your sleeves and let’s begin!


Note: another common toilet leak is when water is constantly running and going into the the overflow tube. In this case, the toilet fill valve is the likely source of the leak. If this is the problem you’re having, then read my post on How to Replace the Toilet Fill Valve.


Step 1: Shut off water to the toilet

White toilet with water shutoff valve in silver, with blue annotated text
A toilet water shutoff valve. Turn clockwise to stop the flow of water to the toilet.

Locate the water shutoff valve – typically located behind and toward the bottom of the toilet. Turn the valve clockwise (until you can’t turn it anymore) to stop the flow of water to the toilet.

Step 2: Flush the toilet to empty water from the tank

Inside of a toilet tank showing toilet fill valve and toilet flush valve and a red toilet flapper
Emptying water from the tank will allow you to remove the toilet flapper (in red) more easily.

Remove the lid of the toilet tank, then flush the toilet. This will empty the water from the tank, allowing you to remove the old flapper and install the new flapper more easily. Note that a little water might still be in the bottom of the tank after flushing – that’s ok! Since we won’t be removing the tank, you don’t need to drain this remaining water.

We will be replacing the toilet flapper, which in this picture is in red (and indicated by a white arrow):

Inside of a toilet tank showing toilet fill valve and toilet flush valve and a red toilet flapper. Blue text and arrows indicate the fill valve and flush valve; white arrow and text indicate the flapper
Toilet flapper (in red) indicated by a white arrow. Toilet fill valve and flush valve are indicated bu blue arrows for reference.

Step 3: Remove the old flapper

Toilet overflow tube in black and toilet flapper in red
A toilet flapper connects to the handle lever (blue arrow) and on both sides of the overflow tube (pink arrows).

A toilet flapper usually connects in three places: a chain that attaches to the handle lever (blue arrow) and on both sides of the overflow tube (pink arrows). Disconnect the chain first so that it is no longer attached to the handle lever. Then unsnap the flapper from the small pegs/studs on the sides of the overflow tube. If it’s a little hard to lift off the flapper from the pegs/studs, or there’s not a lot of space for your hands or fingers to work, you can use a flat-head screwdriver to help unsnap the flapper from the overflow tube.

Here’s what the toilet tank should look like after removing the flapper:

Inside of a toilet tank with no flapper
Toilet tank and flush valve with no flapper.

Step 4: Connect the new flapper

There are several different types of flappers, so make sure you get one that fits your toilet’s flush valve. Here is the Fluidmaster replacement flapper that I needed:

With the new flapper in hand, simply reverse the previous step! Snap on the new flapper on both sides of the overflow tube, then connect the chain to the handle lever.

“Flush” the toilet a few times using the handle (even though no water will enter the tank) in order to test the new flapper. Make sure that it sits securely over the flush valve, and that the chain connecting to the handle lever is at an appropriate length.

Step 5: Turn on water to the toilet

White toilet with water shutoff valve in silver, with blue annotated text
A toilet water shutoff valve. Turn counter-clockwise to restore the flow of water to the toilet.

Return to the water shutoff valve and turn the valve counter-clockwise (until you can’t turn it anymore) to restore the flow of water to the toilet. After the tank has refilled with water, you should no longer hear the sound of running water or see the water level in the tank lowering.

Flush the toilet once or twice to make sure the flapper is working as water flows into and out of the tank. If everything is working, replace the toilet tank lid and you’re all done!


Did you find this guide useful? Let me know in the comments below!


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