How to Replace Your Toilet Flapper
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How to Replace Your Toilet Flapper

How to replace the flapper valve on your toilet when it leaks.

One of the most annoying sounds a homeowner can hear is the repeated filling of their toilet tank at night. In most instances this is caused by a worn out flapper. The flapper is the device in the toilet tank that is connected to the flush handle by a lever and chain that allows the water in the tank to flush the waste down the drain. As it ages, the flapper will begin to leak water from the tank to the bowl and can waste thousands of gallons per year. One cause for leaking flappers may also be toilet bowl cleaners that are added to the tank which may dissolve the rubber flapper or plastic seat.

Check out the Flapper

Remove the lid from the toilet tank and set it aside and place a few drops of food in the tank water. Allow the water and dye to sit for about 10 minutes. Check the water in the bowl of the toilet. If any dye has leaked into the bowl, the flapper valve is likely worn out and is leaking. Replacing the flapper will solve the problem most of the time. You can also make a mark on the overflow tube and check to see if the water level has dropped.

There are several types of flapper valves, but they all do the same job. Some toilet manufacturers use certain designs so you need to know the make of your toilet when you go to buy a new flapper. It is best to take the old flapper with you to the hardware store, but you’ll need to shut off the water to the toilet before doing that.

Replacement Steps

1. Before beginning any plumbing project, locate the main water shut off to the home just in case there’s a major problem. If you haven’t already done so, shut off the water supply to the toilet. The shut off valve is usually located on the left side of the toilet coming out of the wall a few inches above the floor. Be very careful when you turn this valve as it may not turn easily and can break if too much pressure is applied. If the valve won’t turn, you should consider contacting a plumber before proceeding. Older style shutoff valves require several turns to completely shut off the water. These valves have a football shaped handle with a screw in the center. Newer valves may be ¼ turn or ball valves which are easier to use.

2. After the water to the toilet is shut off, flush and hold the flapper open to drain all the water from the tank. You can soak up any remaining water in the tank with a sponge or towel or use a small cup to scoop out the water. You can remove the old flapper by pulling it off the valve posts on either side of the overflow tube.

3. Depending on the type of flapper, the valve seat may also need to be replaced. Some repair kits include an adhesive seat replacement. Whatever the design, you want to make sure the valve seat is clean and smooth. A valve seat that is uneven or has scale buildup will not maintain a good seal.. Attach the new flapper to its posts and attach the chain to the flush handle arm. Make sure the flapper lifts and drops into place smoothly. You may need to adjust the length of the chain connecting the flapper to the flush arm handle to be sure your flapper lifts sufficiently to drain the tank and then seals completely when it drops. Some models slide over the overflow tube down to the seat of the tank. Universal replacements have a molded rubber piece that can be cut off for mounting onto the flapper posts or left intact to slide onto the tube.

Korky Universal Flapper Valve

4. Turn on the water supply to the toilet. Observe the tank as it fills and notice if the flapper seems to be holding a seal. Flush to test.


An old plumber’s trick to fix a slightly leaking flapper valve is to coat the underside of the flapper valve with a thin layer of petroleum jelly. This is water resistant so it will take a long time to wash away and it will fill in any irregularities in the flapper and seat.

To check if your flapper is bad you can also fill the tank and press on the top of the flapper with a ruler or dowel to add a little pressure to the seal. If you don’t hear the water, then you know the flapper is bad.

A glue-in replacement flapper seat glues into the seat of an old metal valve and makes a lasting repair to some valves without removal. Follow the manufacturer's directions.

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Comments (2)

Just what I needed, thank you! I've had a leaking toilet for a month now and it's driving me nuts, but I didn't want to hire a plumber for what seemed like it should be easy to fix myself. Now I know. :)

had to read this because I had no idea what a toilet flapper was! now I know.