fixmyplumbing

The ball float will only turn off the water to the tank or toilet if it floats. In quite rare cases the plastic float cracks or pinholes enough to let water in. If it has water in it the float either sinks or lies quite low in the water so doesn’t set the water level correctly. A new ball float is available here.  To fix this hold the arm of the valve up so the valve stays closed and unscrew the float off the end of the arm.  Screw the new float on and let the arm drop back into the water.