Adjusting the water level in a toilet can usually be done by tweaking the flushing apparatus inside the tank. In order to see what you have to work with, you will first have to lift the lid on your toilet tank to find the flushing apparatus. When the toilet is flushed, the plunger will lift up and the water will rush out the drain. When the flap drops back into place, the water should automatically flow back into the tank until it reaches a certain level. Usually there will be a "floater," a piece of floating rubber or plastic attached to the apparatus, which will signal that the water level has been reached.
Depending on the style and age of the toilet, the floater will look different. Some of them are hollow rubber balls attached to the end of metal or plastic floating arms. When the ball rises on the water to a certain level, the movement of the floating arm shuts off the water. Other times, the floater will take the form of a cup. If you can't see a floater, your toilet may have a floatless apparatus and the water level can be adjusted by means of a screw.
Usually, the floater can be adjusted by hand in order to change the toilet water level. Bending the floater arm up or down will allow there to be more or less water inside a tank. A floater cup will have a clip that can be adjusted for a higher or lower water level. A flushing apparatus without a floater may require a screwdriver in order to adjust the toilet water level sensor.
Sometimes, the floater will have become waterlogged and will no longer float. If this is the case, the floater will need to be replaced. Checking the seals around the water drain is also a good idea. If they are corroded and leaking, water will continue to run continuously in the toilet, making it impossible for the proper toilet water level to be reached.
You may need to adjust your toilet water level for many reasons. The toilet may not be taking in enough water, which will result in incomplete flushing. Too high a water level may run continuously and cost you more money than you can afford. Usually, the kind of adjustments needed to change the toilet water level can easily be done in a few minutes. If your toilet is still not working properly, you may have to have the entire apparatus replaced.