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.

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. 

If your garbage disposal powers up and you can hear it hum, but the arms inside aren’t moving, the problem might be a stubborn clog, a build-up of grease, or a jam of the impeller plate. To troubleshoot these, ensure your unit is off and disconnected from its power source before checking inside the drain or attempting to manually rotate the impeller arms or plate from the underside of the unit. A hex wrench can help.

Replacing a garbage disposal costs anywhere from $150 to $950, but the average cost is somewhere around $550. There are two types of garbage disposal units, and continuous feed disposals tend to cost more than batch feed disposals. Going for an aluminum garbage disposal is also significantly cheaper than choosing a stainless steel garbage disposal. You'll also need to factor in the horsepower of the motor, labor, and the removal and disposal of your old unit.