adjusting a toilet flapper - plumber fixing flapper on toilet tank

Adjusting a Toilet Flapper (So Easy, it’s Only 6 Steps!)

If your toilet runs continuously but the water never reaches the top of the overflow tube, then adjusting a toilet flapper is your first item to check.

This article will discuss the most persistent problem with toilet flappers and how to fix it.

What’s the Problem?

So, why do we want to check the toilet flapper first? It’s simple. We see one problem over and over. Thankfully, it’s an easy one to fix.

Your toilet flapper is probably misaligned with the flush valve seat that it sits on. The flapper (or stopper) needs to sit perfectly on the valve seat (also called a valve or flapper gasket) for the toilet to stop running.

Here’s how it works. When it is raised up, water gets flushed. When it goes back down, it creates a watertight seal on the flush valve seat.

If the seat is misaligned as we suspect, it won’t create that watertight seal, and water will continue flowing. So, the first attempt at a solution is to adjust the flapper’s guide arm. If it continues to run after this, the stopper may be worn or cracked and will need to be replaced.

Adjusting a toilet flapper - simple diagram of basic parts of a toilet tank
This simple diagram shows the most basic parts of a toilet tank. Notice that the flapper sits on top of what’s called a flush valve seat. The flapper needs to be aligned correctly for the toilet not to continue running.

Adjusting a Toilet Flapper in 6 Steps

All you need to do this job is about 20 to 30 minutes and the following tools: sponge, slip joint pliers, and a scrub pad.

  1. Begin by turning off the water supply valve. It is usually a round handle that can be found under the toilet tank, against the wall on the left side.
  2. Now, flush the toilet to empty the tank and sponge dry the tank.
  3. Look at the lift wire to see if it is bent. If it is, bend it straight again with your hands. The lift wire can be seen in the diagram below.
  4. Using your slip joint pliers, loosen the guide arm adjustment screw. Adjust the guide arm back and forth as necessary so it guides the flapper directly into the flush valve outlet. Then retighten the guide arm adjustment screw.
  5. Pull up the flapper and clean the inside of the flush valve outlet. Do this by scouring it with your scrub pad. We want to make sure the flapper and flush valve seat are nice and clean for a perfect fit.
  6. Finally, drop the flapper into position and turn on the water supply valve under the toilet tank.

PRO TIP: Sometimes, the problem is the float that’s attached to the toilet flapper chain. You can adjust the float too. Here’s a video that explains this simple process.

You can also view this related video here.

What if the Flapper Has a Crack Or Is Wearing Away?

If you find that the toilet flapper has a crack or is wearing away, then you’ll need to move onto the next step: replacement. But don’t worry, we have some articles on how to do that too. See the “Resources” section below.

adjusting a toilet flapper - man holding a worn out toilet flapper or toilet stopper
Often, a toilet flapper won’t align with the flush valve seat because it is worn out or cracked. This is an example of an extremely worn-out flapper. But it doesn’t have to be nearly this bad to cause toilet running problems.


Here are some great resources for adjusting, fixing, and replacing a toilet flapper. Also included is an in-depth article on how to replace a toilet handle system (which can be a related problem).

Final Thoughts

Obviously, there are many reasons for a toilet to not work properly. So, being able to diagnose the problem is the first step.

For most DIYers, you’ll want to start by checking if your toilet flapper needs an adjustment. Firstly, open the toilet tank, flush the toilet, and see if water ever reaches the overflow tube. Then check the flapper. Does it seem to fit well on the flush valve seat?

If you see that one or both are issues, follow the instructions above for adjusting a toilet flapper in 6 steps.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help with a toilet adjustment, replacement, or new installation.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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