Your garbage disposal is not draining because it might have a clog due to food waste, a foreign object, grease, oil, fat, or it may have a broken motor. When water doesn't flush out of the disposal, that's a key sign that your disposal has a clog or needs repair. 

While the drain connection for a garbage disposal is nearly universal and fits standard sink drain holes of 3 1/2 to 4 inches, the size of the disposal unit itself is not. You must have enough space in the cabinet underneath your sink to accommodate the disposal's housing. A larger model may not fit in a compact cabinet or if the existing plumbing is arranged in an unusual way. Before buying a new garbage disposal, measure the available space under your sink. If you are replacing an old unit, it's often easiest to choose a new model of a similar size.

The main issue with garbage disposals is clogging. This can mean a clogging of the pipes that expel the food along with water, or a clogging of the mechanical parts themselves. The problem lies in the solution because you can’t easily see clogs if they’re inside the system, and reaching in to dislodge stuck items is a risky proposal. Call a pro and ask what they would do, but if you can’t see the clog easily, and running the unit won’t free it, you need to let a professional handle the fix. 

Soil is just one of the items you shouldn't put down a garbage disposal. Garbage disposals are only meant for soft, non-fibrous foods. Large amounts of topsoil, dirt, or rocks will damage the blades of your garbage disposal or clog the pipes. If a small amount of dirt goes down the drain as you repot a plant, you shouldn't have to worry, but never dump a whole pot of soil in the sink for fast disposal.