Fixing Toilet Flapper That Stays Open Too Long (Step-By-Step Guide)

There are a lot of working components in a toilet, and unfortunately they can’t fix themselves. One of these essential parts is a flapper, and when this doesn’t close correctly, your toilet will run continuously.

Most of us are familiar with the annoying sound a running toilet makes. Even worse is the water bill that results from this wasted water. To save yourself the nuisance of a running toilet, and an expensive water bill, it’s best to troubleshoot and fix this problem as soon as possible.

The most common reason a toilet flapper stays open too long is that the connecting chain is too short. Mineral buildup and a warped flapper can also cause this problem. The required repairs are simple and can be completed without special tools.

These problems are common, and most of us will have to deal with them at some point. Here, we will explain how these problems occur, plus how to diagnose and fix it.

What is the Toilet Flapper and How Does It Work?

A toilet flapper is an essential part of the toilet that regulates water flow. This disc-shaped, rubber component is attached to the flush assembly. The flush assembly is a collection of parts that includes the handle we push down on to flush the toilet, an arm on the inside of the tank, and a chain connected to the arm and the flapper.

When we push down on the flush handle, it begins a chain reaction that moves the arm, which in turn pulls the chain, which in turn raises the flapper. When raised, the flapper allows water to flow out of the tank and into the toilet bowl, allowing the contents of the toilet to flush.

The flapper is just one component that is involved in flushing, but if it malfunctions, the process can’t be executed correctly. There are a few different things that cause a flapper to malfunction, and we will cover them, plus ways to fix it.

First, we need to figure out whether your flapper is the problem. A good way to know this is whether your toilet is “running”. Most of us know what this sounds like-a continuous flow of water through the supply line that goes into the toilet tank. When your toilet flapper stays open for too long, water is continuously flowing into the toilet bowl, causing the tank to constantly refill.

Another way to check is to remove your tank lid and do a test flush. Watch the flapper to see when it closes. If it doesn’t close all the way, or takes longer than a few seconds to do so, it isn’t working correctly. 

Also check the shape of the flapper. The flapper should be circular without irregular or wavy edges. A warped flapper can prevent a good seal on the flush valve, allowing water to continuously flow into the toilet bowl.

Reasons Why the Toilet Flapper Stays Open Too Long

Now that you know there is a problem with the flapper, it’s time to troubleshoot. Here are the most common reasons why the flapper isn’t working correctly, and how to fix it.

The lift chain is too tight or too slack

If the chain is too tight, it will prevent the flapper from seating in the flush valve. Look to see if there is any slack in the chain. If the chain is taut, you know it’s too tight.

A chain that is too slack can be problematic, too. The excess chain can get caught on another component in the tank, or create a block under the flapper. This block prevents the flapper from closing completely, and allows water to flow into the bowl.

Luckily, this is a very easy fix. With just a slight adjustment, the repair is done.

Lift Chain

Step 1:  Locate the end of the chain attached to the arm. Using the hook attached to the chain, unhook the chain.

Step 2: Using the holes in the arm, adjust the length of the chain. Generally, the lower hole will loosen the chain, and the higher hole will tighten the chain. 

Step 3: Once you make your adjustment, do a test flush to make sure the chain is now the right length. Adjust again if necessary.

Your repair is now complete! 

Mineral buildup around flush valve

If your chain length is correct, and not hindering the flapper from seating correctly, buildup from hard water may be the culprit. Unfortunately, there are several problems associated with hard water.

Hard water has a high mineral content, and these minerals build up over time. This buildup can form around the flush valve where the flapper sits, preventing a good seal and in turn allowing water to continuously flow into the toilet bowl.

Troubleshooting this problem is a bit more involved than it was to check the chain since mineral buildup isn’t always visible from above the toilet tank. You can pull the chain to raise the flapper, then feel around the flush valve for buildup that way. 

If you do feel buildup around the flush valve, you’ll have to clean it to reestablish a seal around the flapper. The only thing you’ll need for this is an emery cloth, and here are the steps to take.

Turning the Flush Valve

Step 1: Turn off the water supply to your toilet by turning the knob on the water line next to the toilet. 

Step 2: Evacuate the water in the tank by flushing the toilet. There may be some residual water at the bottom of the tank, but this shouldn’t get in your way.

Flushing the tank

Step 3: Pull the flapper out of the way. Now scrub off the mineral buildup with your emery cloth. When the buildup is gone, the flush valve will be smooth.

Step 4: Seat the flapper on the flush valve and check that there is a good seal. If it looks like you removed all of the buildup, turn the water supply back on and to a test flush. 

If everything is working normally, your work is done. However, if the toilet is still “running”, your problem might be the flapper itself. Next, we’ll go over how to replace the flapper.

Hardened or warped flapper

Toilet flappers are made out of rubber, which is a great material. As we know, rubber can harden or warp over time. 

When a flapper hardens, it might not seat completely over the flush valve. This prevents a good seal, and allows water to continuously slow.

If a flapper becomes warped, the shape may not fit perfectly over the flush valve. This warping can leave a gap between the flush valve and the flapper, allowing water into the toilet bowl. 

Toilet Flapper

Replacement flappers are available at all hardware stores, and are very cheap. To make sure you’re getting the right one for your toilet, it’s a good idea to bring your old one in for comparison. Flappers aren’t interchangeable, so save yourself some time and frustration by getting the right one the first time.

Here are the steps to replacing your new flapper. While this repair is a bit more involved than the others we discussed, you won’t need any special tools.

Step 1: Turn off the water supply to the toilet by turning the knob on the water line next to the toilet. Now evacuate the water from the toilet tank by flushing the toilet.

Step 2: Using the attached hook, disconnect the chain from the flapper. Remove the flapper from the mounting pegs that anchor it. Now you can bring the old flapper to the hardware store to pick out your new one.

Step 3: Once you have your new flapper, make sure it seats correctly in the flush valve. Attach it to the mounting pegs, and attach the chain to your new flapper. 

Step 4: Turn the water back on, and do a series of test flushes. Adjust the chain if necessary.

That’s it, you’re done! If there is still a problem after the repairs, it’s best to call a professional. There might be a bigger issue or your toilet might need several components replaced.

When Should You Call a Professional? 

As we mentioned before, if none of these fixes work to solve the problem, it’s best to consult a professional plumber. They can diagnose more complicated problems with your toilet, and quickly fix them.

Professionals have all special tools and supplies needed for these repairs, which relieves you from the stress and expense of gathering everything required. They are also equipped to deal with larger problems that require the dismantling of the toilet.

How Much Does it Cost To Fix a Toilet Flapper?  

If the required fix is one of the repairs we discussed, and there aren’t more complicated problems, it is much cheaper to fix a toilet flapper yourself. Replacement flappers only cost between $5 – $10, while hiring a professional can cost anywhere from $50 – $250. 

Of course, this is only the case if a simple replacement is needed. Bigger problems will require more tools and parts.


A malfunctioning toilet flapper is a common issue that most homeowners will face at some point. Like we mentioned before, it’s natural for parts to break down over time. Luckily, toilets are designed in such a way to make these repairs easy and inexpensive. 

Leave a Comment