Why Does Toilet Flapper Stays Open? (How To Fix It)

Malfunctioning toilet flappers lead to several different issues, including running or overflowing toilets. These issues usually arise from the flapper not closing properly or at all, which means water will continue to flow into the toilet bowl. There are a few different reasons why this might happen.

Toilet flappers stay open due to issues with the chain, the flapper seal, or another part of the flush assembly. These issues are often resolved with a simple repair, but in other cases, the flapper may need to be replaced.

Why Does Toilet Flapper Stays Open

If you hear your toilet continuously running or hear it flush on its own, there may be an issue involving the flapper mechanism inside the tank. Below, we’ll go over some of the different scenarios that create this problem, as well as some DIY tips for fixing it.

Reasons Your Toilet Flapper Won’t Close

If you run your finger where the flapper meets the bottom of the tank and feel any gaps, it’s possible that the flapper isn’t closing properly.

Most commonly, toilet flappers won’t close for the following reasons:

  • The chain needs to be adjusted or replaced.
  • Excess residue build-up.
  • Too much air pressure.
  • Wrong size or weight of flapper.
  • The flapper is broken.

Let’s take a closer look at these reasons.

Why Does Toilet Flapper Stays Open

1. Chain Needs To Be Adjusted or Replaced

The chain that attaches to your flapper is what lifts it up and down each time you flush, and when the chain is faulty, it is frequently the cause of an open flapper.

To test, reach down into the tank and check the tension of the chain.

If the chain is very tight, there may not be enough slack to allow the flapper to close all the way, but if the flapper issue was sudden, it’s possible that the chain is caught up on itself.

However, if somebody recently worked on the toilet, they may have improperly installed the chain.

Luckily, this is usually fixed with a simple adjustment.

All you need to do is change the connection point to a different chain link to create a little more slack.

2. Excess Residue Build-Up

Another possibility is that residue has built up in the tank, which is especially common if you have hard water.

Residue, sediment, or water minerals sometimes harden around the flapper hinge, preventing it from opening or closing fully.

Other times, residue may build up on the underside of the flapper itself, which might keep it from sealing all the way around.

3. Too Much Air Pressure

Also, air pressure is sometimes an issue.

If too much air gets caught in the piping, the flapper may be forced upward.

This is sometimes temporary until the air works its way out, but it may last for a little while if the air gets stuck.

4. Wrong Size or Weight of Flapper

If the size or weight of the flapper is wrong, it won’t seal properly, so if yours has recently been replaced, it’s possible that this is the issue.

The flapper sits in the tank full of water, so it must be heavy enough to sink and seal the gap between the tank and the pipe leading to the toilet bowl.

If your flapper is sticking upward despite having sufficient slack from the chain, it may not be heavy enough.

Also, the flapper should sit firmly on top of the opening, so if you’re able to push it downward at all, there may not be enough weight.

Additionally, toilet flappers must be properly sized. While there are generally just a few different sizes, a flapper that’s too small or too large may leave a gap for water to flow.

5. Flapper Is Broken

The flapper itself may just be broken, which is particularly possible in older toilets, as the rubber in the flapper may crack or tear.

If the damages are severe enough to break the seal, the flapper would need to be replaced.

READ: Toilet Tank Anatomy (8 Components Explained)

Tips for Fixing Your Toilet Flapper

Why Does Toilet Flapper Stays Open

Fixing a toilet flapper that won’t stay closed will depend on what the issue is.

Some tips for fixing it yourself include:

  • Adjust the chain: If the chain is too short, you’ll need to change the spot at which the chain connects to create more slack.
  • Clean off the residue: This is often easier if you shut off the water and empty the tank. You can wipe away residue while the flapper is connected, or you can remove the flapper and soak it in vinegar or another cleaning agent.
  • Add weight to the flapper. Instead of buying a new flapper, you may be able to just add weight to it. You can hang a weight from the chain or put a metal washer around the chain so that it rests on the flapper.

However, sometimes, the flapper may not be able to be fixed, but in certain situations, it might be easier just to replace.

How Do You Know You Need a New Toilet Flapper?

Why Does Toilet Flapper Stays Open

If you’ve determined that the toilet issue is related to the flapper mechanism, you’ll have to decide whether you’re going to fix or replace it.

You’ll need a new toilet flapper if the current piece is physically damaged or is the incorrect size or weight. If the chain is broken, it may be easier to buy a new kit as well.

The other thing to keep in mind is the seal at the bottom where the flapper sits.

If the toilet is older, the seal may be warped to the point that a brand new flapper may not conform to its shape. If this is the case, you may have to purchase a more extensive repair kit that comes with a replacement seal.


Toilet flappers stay open for a handful of different reasons. Sometimes it’s as simple as a chain adjustment, and other times, you may need to replace the entire flush assembly.

If you have a little bit of DIY knowledge, you might be able to fix most flapper issues on your own.

However, if you’re not sure what the issue is or how to fix it, it may be best to call a professional for a proper solution.

Cheers, tools owners!

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Hi there! My name is Jack and I write for ToolsOwner. I have a passion for everything related to tools and DIY projects around the house. You often find me in my workshop working on new projects.