If you’ve ever lifted the lid on the tank of your toilet, you’ve most likely seen the toilet float. The float is the device that allows the water to fill the tank but prevents it from overflowing. Also called a float valve or ballcock, older-style floats consist of a plastic ball attached to a metal rod. Earlier floats were made of brass or copper and may still be in use. The newer type of flushing mechanism works by using a float cup, a round cylinder that rides up and down on a vertical arm.
No matter which type of toilet float you have, they all work essentially the same way. When the toilet is flushed, the water rushes out of the tank and the float drops, allowing fresh water in to refill the tank. As the water rises, so does the float; once the tank reaches its fill level, the float will shut it off. This simple mechanism can work trouble-free for years on end, but toilet parts can occasionally break or wear out and a toilet float is no exception.
If the water in your toilet unexpectedly runs and turns off on its own or runs continuously, there are several possible causes that may be connected to the float. A ball float can develop cracks over time and begin to fill with water. Once this happens, it will ride lower in the water and cause the toilet to run. Sometimes you just need adjust the toilet float by bending the arm down slightly to stop the water from running.
Of course not every problem with a toilet is caused by the toilet float. Another possible problem is the tank ball, a small rubber plunger-shaped cup that sits over the hole in the bottom of the tank. When the toilet is flushed, the tank ball acts as a stopper to let the water out or to hold it in. These wear out over time and lose their seal. In this case, attempting to adjust the toilet float won’t stop the water from running and the tank ball will need to be replaced.
Toilet repair is fairly easy for most do-it-yourself homeowners and a toilet float is not difficult to replace. They are usually just screwed on to the metal arm. Of course if you’re not handy with simple tools or feel squeamish about reaching into the tank, you may want to ask a friend for help or call a professional plumber.