Most people have had a "running" toilet at one time or another. With a running toilet, you can hear the trickle of water that is leaking from the toilet tank into the toilet bowl and the hiss of water passing through the pipes to refill the toilet tank. The sound of a running toilet is bothersome, but the real problem is that it wastes many gallons of water daily.
Before reading through the following information, please check out the diagrams on How a Toilet Works & Toilet Plumbing Diagrams so you understand the names of the various toilet components.
More often than not, water leaks from the tank into the bowl because of an aging or defective flapper or tank ball that doesn't seat properly against the flush valve between the tank and bowl. Water can also continually drain from the tank into the toilet bowl if water rises too high in the tank and spills into the top of the overflow tube.
In some circumstances, it may not be entirely obvious that the toilet is leaking water into the bowl. But if you hear a hissing sound or the ball cock repeatedly refilling the tank because the water level in the tank is dropping, the chances are good that it is leaking water into the bowl.
To fix the problem, you have to determine whether the water is entering the bowl through the flush valve or the overflow tube. You can do this by simply removing the lid from the tank and looking at the overflow tube. If the water has filled the tank to the top of the tube and is spilling into it, this is the problem.
Water Leaking Into Overflow Tube
For a toilet with an older-style float ball flushing mechanism, try lifting the float ball above water level. If this shuts off the flow of water, simply bend the wire that holds the float ball (called the float arm) slightly downward so it shuts off the water sooner--when the water level is about 1/2 inch below the top of the overflow tube.
In some cases, particularly with an old toilet, the float ball may have leaked and filled with water so it doesn't float properly. If you suspect this to be the case, turn off the water supply valve behind the toilet and flush the toilet to empty the tank. Then lift the ball to see if it feels full. You can also unscrew it from the float arm and shake it. If it has water inside, replace it with a new float ball or--even better--replace the entire flush valve mechanism with a newer model.
If your toilet has a pressure-activated ball cock instead of a float ball, turn the adjustment screw on the valve to slightly lower the water level.
Toilet Flush Valve Leaking
The quickest (and most common) fix for a running toilet is to simply jiggle the flush handle. More often than not, this re-seats the flapper or float ball in the flush valve. Tank balls are common in old toilets; flappers are typical for new toilets.
To test whether or not water is leaking through the flush valve, you can squeeze a 2 or 3 drops of food coloring into the water in the tank, wait a few minutes, and check the water in the bowl to see if the color has reached it. If it has, the flapper is leaking.
The mechanism that holds the older-style tank ball can become misaligned. Reach in and wiggle the tank ball to make sure it is free to move up and down directly over the flush valve. If it doesn't move freely through its holder, try polishing it with some steel wool. Be sure the lift wires are properly connected. If this doesn't do the trick, you may need to replace the tank ball mechanism with a flapper.
But before you do, make sure the lift chain hasn't become snagged or kinked. When this happens, the flapper or tank ball can't drop down all of the way to form a proper seal. With a flapper, also check the two rubber ears that connect it to the collar to make sure it hinges up and down.
Before you make repairs inside the tank, turn off the water supply to the toilet at the shut-off valve located behind it and flush the toilet once to empty the tank's water.
You can buy replacement flappers that will fit most toilets for under $10. Most come with installation instructions. With most, you remove the old tank ball or flapper, slide the new flapper's collar down the tank's overflow tube, center the flapper over the valve seat, and hook the lift chain to the trip lever with a little slack in the chain.
Make sure the flapper flops up and down easily. Then turn on the water supply shut-off valve to refill the tank and test the flapper for proper flushing. If it closes too quickly, adjust the length of the lift chain by pulling it tight and then backing it off one link.
Some toilets have a corroded flush valve seat that will continue to leak even after replacing the flapper. If this is the case, you have two options: 1) Scour the flush valve seat with steel wool or a special tool made for this purpose to smooth it out or 2) replace the entire flush valve seat assembly, which is a considerably bigger job. If you decide to do this, follow the instructions that come with the valve seat replacement kit.