The water level of a toilet is adequate if it is approximately 1 inch below the opening of the overflow tube. Otherwise, enough water may not fill the bowl. To check the water level, the tank cover must be removed after the fill valve has shut off.
Multiple causes contribute to an insufficient water level of toilet bowls, including partial clogs, an insufficient amount of water in the tank and obstructed vent pipes. If a water leak occurs resulting from a crack, the toilet must be replaced. An inordinately high level of water is usually the result of a clog and is easily correctable through use of a plunger or toilet auger.