When a dishwasher discharges its wastewater, it uses a pump to quickly move a lot of water. If anything in the drain line or the garbage disposal impedes the high volume of water, it will back up into the sink through the drain or the garbage disposal. Following regular dishwasher maintenance tips like clearing clogs, keeping them cleared, and occasionally running the disposal will eliminate the problem.

On average, a garbage disposal can last anywhere from 7 to 12 years, with many models functioning well for about 10 years. With heavy usage, a motor may last a minimum of five years, while grinding plates will wear down over time. It's generally a good idea to consider a replacement if your unit is approaching the 10-year mark. Other signs that it's time for a new disposal include frequent leaks, persistent clogs, lingering odors, lack of power, or unusual noises. If your unit is not that old, it's worth investigating if a less expensive part, like a rubber seal or a loose hose, is causing the issue.

These appliances certainly increase the number of things allowed down the drain, but they’re not foolproof. There are several items you shouldn’t put in your garbage disposal, according to manufacturers and technicians. Don’t put coffee grounds down the drain. The same goes for eggshells, potato peels, hard foods, onion skins, and any dry, expandable food. Most importantly, never put grease or oils down the drain.

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.