Step 4 · Test the Adjustment

After making an initial adjustment, you must test the new water level. Flush the toilet by pressing the handle. Allow the tank to completely refill with water. Watch the water level as it rises. The fill valve should now shut off completely when the water level is approximately 1/2 to 1 inch below the top of the overflow tube. If the water still rises too high and enters the tube, repeat Step 3 to lower the float a little more. If the water level is now too low, resulting in a weak flush, adjust the float slightly higher. Repeat this test until the water shuts off at the correct level.