Adjusting the toilet water level involves adjusting the float valve. This valve regulates water flow into the tank to ensure the water level is at the best level for optimal toilet flushing. There are two primary float valve types — concentric valve type and the ball-cock valve type — both of which require the removal of the tank cover to gain access.
To adjust a ball-cock toilet, push the ball float down and use the rod's inner end adjustment screw to alter the water flow if water is running. Go to the top of the valve and turn the vertical adjuster screw. Turn the screw one full rotation while lifting the ball and until the water stops running, let the ball float. Flush the toilet, and observe the water level and the flush power to determine if further adjustment is necessary.
To adjust a concentric valve toilet, identify the concentric float by flushing the toilet. At the adjustment rod's upper end, there is a small nut that has to be loosened. On average, just two to three rotations is adequate. Observe the flush power and the water level by flushing the toilet. If the water level is not desirable, simply repeat the process until it is.