If you are referring to the level in the bowl. The only adjustment for it, is in the tank. The tank has a tube that stretches from the top of the fill valve and transfers water into the overflow tube in the middle of the tank, to refill the bowl after every flush. Bowls are emptied completely by syphon. The only way they are refilled is with the fill tube. When it sits for a long time, some of the water evaporates out of the bowl. If it doesn't refill after you flush it, then check to see if any water is flowing throught this 1/4" tube. It should have a steady stream of water running through it. Pull it up out of the overflow tube when the toilet is refilling to test its flow. If there is no water flowing through it, or its not in the overflow tube, you may have to figure out why. The fill valve may be clogged with sediment, preventing water from going into the fill tube.

Good Luck

Raymond VinZant Plumbing Prof.