How to Fix the Flapper on Your Toilet's Flush Valve

By
Bob Formisano
Bob Formisano
Bob Formisano is a licensed architect and builder with nearly 40 years of experience building new homes and restoring older homes. One of his specialties is repairing old systems dating back to the 1920s, including galvanized water pipes, knob-and-tube wiring, and more. His home repair articles for The Spruce span more than 10 years.
Learn more about The Spruce's Editorial Process
Updated on 08/03/22
Reviewed by
Richard Epstein
Richard Epstein
Reviewed by Richard Epstein
Richard Epstein is a licensed master plumber with over 40 years experience in residential and commercial plumbing. He specializes in estimating as well as design and engineering for plumbing systems, and he works for one of New York's largest union plumbing construction companies.
Learn more about The Spruce's Review Board
Toilet handle pushed down with flush valve flapper lifting in tank

The Spruce / Kevin Norris

Project Overview
  • Working Time: 5 mins
  • Total Time: 5 mins
  • Skill Level: Beginner

When your toilet starts acting up, you might immediately start wondering how much it will cost to get a plumber out to fix the problem. The good news is that there are several simple problems that can occur with a toilet, and most of them are an easy fix. A straightforward toilet part known as the flapper is responsible for two of the most common problems with toilets. Learn how to identify and fix flapper issues on your toilet's flush valve.

What Is a Flapper?

The flapper is a contraption in the toilet's tank that's responsible for draining water from the tank into the bowl when you flush. In some cases, the flapper is attached to the tank by a chain; when you flush, the handle moves the chain, which lifts the flapper, allowing water to pass.

The modernization of toilets has allowed for many variations of the flushing mechanism or flapper. The same general process still applies, but in most cases, you should look to replace the flushing mechanism with factory parts (following manufacturer instructions) to ensure you're using the proper pieces and following the correct steps.

Before You Begin

Remove the cover from your toilet tank and look down at the large opening in the bottom of the tank. This is the flush valve, and in normal operation, there is a rubber or vinyl flapper designed to lift up away from the flush valve when the toilet handle is pressed to start the flush cycle. At the end of the cycle, the flapper is supposed to settle back down into the flush valve opening and seal it tightly until the next flush cycle is initiated.

There are two situations that tell you the flush valve is not working correctly. If the toilet doesn't flush completely unless you hold the handle down, it is usually because the flapper is not lifting fully away from the flush valve. If the toilet flushes just fine but continues to run, the flapper probably does not fit properly into the flush valve opening.

Very old toilets may use a tank ball with a lift rod rather than a flapper and lift chain to seal the flush valve opening. Consider replacing the flush valve unit with a more modern assembly. Modern kits offer a single piece that includes the flush valve, the refill tube, and the flapper in a single unit.

It may be necessary to turn off the water when working inside the tank. Although professionals can work without shutting the water off when replacing a flapper, it may be easier for DIYers to shut the valve below the tank off.

What You'll Need

Equipment / Tools

  • Cutting pliers

Materials

  • Flapper or flapper repair kit

Instructions

Materials and tools to fix flapper in toilet flush valve

The Spruce / Kevin Norris

Fix a Toilet That Won't Fully Flush

One of the most common toilet problems is having to hold the flush lever down completely to flush the toilet. The problem is caused by too much slack in the lifting chain that connects the flush lever to the flapper. When the chain has too much slack, it cannot lift the flapper high enough to allow the full amount of water to flow down through the flush valve; it closes prematurely, stopping the flush.

  1. Adjust the Chain Length

    Locate the chain in the toilet tank. Adjust the chain length until there is only about 1/2 inch of slack.

    Flapper chain held in hand inside toilet tank

    The Spruce / Kevin Norris

  2. Test the Operation

    Flush the toilet. It should fully flush. If it doesn't, adjust the chain again.

    Toilet handle pushed down to test flushing

    The Spruce / Kevin Norris

  3. Trim the Chain

    The chain might now be a bit too long and hanging down. If the leftover chain hangs down too far and interferes with any part, trim the length of it with cutting pliers.

    Flapper chain trimmed with cutting pliers inside toilet tank

    The Spruce / Kevin Norris

Fix a Toilet That Continues to Run After Flushing

Sometimes water in the toilet tank will continue to flow even after the flush is completed. The problem is annoying, and it can waste hundreds of gallons of water if it isn't fixed.

This usually is caused by another issue with the flapper. When the flapper doesn't tightly reseal against the flush valve, water will continue to flow down into the toilet bowl. Because the water level in the tank never reaches the level necessary to shut off the water supply valve (ballcock), water continues to flow.

  1. Check the Lift Chain

    Make sure the lift chain is not so long that it pinches between the flapper and the flush valve. If it is, water will leak down into the toilet bowl after the flush. Shorten the chain slightly so it doesn't get pinched beneath the flapper.

    Lift chain attached to flapper checked inside toilet tank

    The Spruce / Kevin Norris

  2. Align the Flapper

    Make sure the flapper is properly aligned so it seals correctly against the flush valve opening. You may be able to make small adjustments to the flapper that stop the leaking.

    Flapper aligned with flush valve opening in toilet tank

    The Spruce / Kevin Norris

  3. Replace the Flapper

    If the rubber of the flapper is old and cracked, it will be unable to seal the flow of water into the tank. In this case, you'll need to replace the flapper. Or, you can replace the entire flush valve/flapper assembly with a convenient repair kit.

    New flapper replaced inside toilet tank

    The Spruce / Kevin Norris

1:53

Watch Now: How to Replace a Toilet Flapper