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Repairing A Leaking Toilet Flapper Valve

Between flushes, my toilet makes a noise like water is running into it. What is happening and how do I fix it?

The most likely problem is that water is leaking around the flapper in the bottom of the toilet tank. When the water in the tank drops to a certain level, the intake valve thinks "Duh... somebody musta flushed, so I better turn on and fill da tank!" The valve turns on, but since the water level has only dropped a few inches at most, it only stays on for a few seconds, till the level is back up to normal.

Before you replace the flapper, lift it up and run your finger around the flapper seat. Are there any bits of stuff stuck to the seat? If so, dislodge them and see if that solved the problem. If your hands became blackened from handling the seat or the flapper, then you have found your answer... the flapper is dissolving and must be replaced.

Chlorine or acids in the water cause rubber flappers to deteriorate.  In-the-tank automatic toilet cleaners generally contain so much chlorine that they will destroy the flapper (and all other seals and gaskets), making it twist and distort.  This causes a poor seal leading to intermittent and eventually constant leakage.


The flapper is a little rubber workhorse., and replacement of a flapper is one of plumbing's easiest jobs. But, in deference to Murphy's Law, exercise some caution in removing the old flapper and installing the new one. If you break any plastic parts, you may be in for a more extensive repair than you bargained for!! The skinny of flapper repair is to simply pull the flapper off of the mounting 'ears', or unscrew or unsnap it from its mount. Put the replacement back in the same place. The chain of the new flapper should connect in the same place as the old one. Of course, life isn't always that simple. There are a few types of flappers, and each one requires a slightly different installation procedure.

Types of flappers and their installation...

It is a good idea to turn the water off to the toilet before replacing the flapper, though you can replace some styles in under a minute! Just one less distraction from doing the best job you can.

Rubber flapper

This is by far the most common type of flapper, available from many manufacturers in various styles and appearances. Some are made entirely out of rubber, and some, such as the Bulls Eye® flapper from Fluidmaster® , use a solid plastic framework with an integral rubber seal. Both types of flappers clip onto little ears at the base of the overflow pipe.

When you attach the flapper chain to the flush arm, it should be just slightly loose, so the flapper closes completely. If the chain is TOO loose, the flapper will not be lifted high enough to "float", and will not stay open without you holding down the flush handle.

One peculiarity with flappers is that on some toilets, one style of flapper might work while another one will not. So if you replace the flapper, adjust it correctly, clean the seat, and it still doesn't seal... don't cry, just purchase another brand or style of flapper and try again!

Tank ball:

a ball-shaped rubber flapper that moves vertically when flushed, pulled by a threaded lift wire attached to the trip arm. To replace, unscrew the ball from the lift wire and replace with a new one. Unlike the other flappers discussed here, this one can go out of adjustment. There is a guide arm through which the lift wire travels, and it must be directly centered over the flapper seat or the flapper may leak.

Is your seat disk snap-on or threaded?

This is an older style American Standard flapper... a circular disk about 3 inches across. It is attached to a fairly large plastic assembly, hinged at the base of the overflow tube. Attached to it is a small cylindrical reservoir or cup which is filled with water. When the toilet in flushed, the entire framework tips back, lifting the attached flapper disk. The reservoir acts as a counterbalance to the flapper disk, and holds the flapper open. The reservoir begins to empty itself through small holes in its base. Once it is sufficiently empty, the plastic framework falls back to its closed position, firmly seating the flapper disk in the seat. by this time, the toilet tank has drained and is ready to refill.

The seat disk flapper comes in two styles, threaded or snap-on. The biggest problem working with either of these is that you don't have much room in the toilet to work. Since you risk of breaking the entire enchilada if you try to remove the assembly from the tank, it's usually best to do the repair in the tank, and be careful!

Use a flashlight, with a small inspection mirror if necessary, to see how the old disk is mounted. If you can see a small threaded bolt holding the disk on, grab the top of the bolt with a pair of small pliers. Spin the disk off counterclockwise. Looking from the top, counterclockwise LOOKS clockwise. Then you can screw on the new disk.

The snap-on type can be a little tricky if the flapper has hardened from years of chemical assault from chlorine. Twist the flapper on the base to loosen it from the knob, then rock and wiggle it to soften it up. After working it for a minute, you can start trying to ease it off of the knob it has been pressed onto. Just be patient and keep working at it.

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