Garbage disposals are designed to take a lot of abuse, but nowhere near what some people put them through. As magical as they seem, these powerful machines do have their limits—and if used improperly, you can do just as much damage to your plumbing with a disposal as you can without one.
Everyone knows that certain things don’t belong in a garbage disposal, but it’s surprisingly hard to get a straight answer about what exactly those things are. The easiest way to separate the things that can and cannot go down the disposal is to have a general idea of how they work. Lots of people think that garbage disposals have spinning blades like a blender, but they’re actually closer to flat burr coffee grinder. As the motor turns, it forces food particles in the main disposal chamber through a series of holes around the perimeter, breaking them up into tiny particles. From there, the food flows into the wastewater pipe and on its merry way:
Ultimately, your garbage disposal is just a fancy front door to your kitchen sink: everything you put down it eventually ends up in your pipes, just in much smaller pieces. In order for a piece of food to go from the garbage disposal to the waste water treatment plant with no major detours along the way, it needs to be soft enough to pass through the grind holes and water-soluble enough to resist clogging. This covers most things you’d eat, but as always, there are some notable exceptions.
Non-food items
This should be obvious, but never put anything that isn’t food down your disposal. It’s designed to break down stuff that’s soft enough to chew—not glass, metal, or even paper. The first two are easy enough to avoid, but don’t forget to peel off stickers and labels from produce or new kitchen gadgets and throw them in the garbage. While one or two won’t do much damage, they can build up over the years.
Anything really hard
Your garbage disposal is a powerful grinding machine, but that doesn’t mean it can handle anything you feed it. The really tough stuff—think fruit pits, bones, raw meat, and fruit or nut shells—won’t break down at all. Instead, it’ll just bounce around the chamber, getting more and more banged-up until you admit defeat and chuck it in the trash or compost where it belongs. If it’s too hard to chew, it’s too hard to grind up.
Of course, just because your disposal can grind something doesn’t mean it should. Egg shells are a great example of this: most disposals will eventually break them down, but they pose more danger to your pipes than the disposal itself. The shards don’t exactly dissolve in water, so they’re prone to building up over time and even clogging your pipes.
Known clog risks
On that note, it’s extremely important to avoid putting potential clogging agents down your disposal. These are the worst offenders:
Grease and oil: Never put large quantities of oil down any drain, not even one with a disposal. Cooking grease floats on top of waste water, sticking to the walls of your pipes and trapping particulate solids until it forms a massive plug. Let frying oil cool and dispose in the trash—or strain it and re-use.
Coffee grounds: Where fat floats, coffee grounds sink. Even if they don’t get caught in built-up grease deposits, they can collect on the floor of pipes, eventually stopping the flow of water altogether. Throw them away, compost them, or save them for garden fertilizer.
Anything that can absorb a lot of water: Cooked or raw rice, bread, pasta, grains, flours, and starches are far too water-absorbent to safely pass through pipes.
Anything that can get stuck in a pipe probably will. When in doubt, think about what would happen if you left that thing in a bowl of water indefinitely. If it would dissolve on its own, it’s probably OK; if it wouldn’t, don’t risk it.
Fibrous or stringy substances
Thanks to good old common sense, most people know enough not to put chicken bones down the garbage disposal—but might think nothing of chucking in a stalk of celery. Unfortunately, some fruits and vegetables are so fibrous that their surprisingly tough structures don’t always break down in the disposal. Over time, stringy fibers from foods like celery, corn husks, pineapple, onion and garlic skins, asparagus, and artichokes can get tangled, putting unnecessary stress on the motor and shortening its lifespan.
Too much of anything
As is so often the case, when it comes to garbage disposals, the dose makes the poison. Even innocuous foods like carrot peels can cause problems if you cram your disposal full of them and then switch on the motor. Always run the tap, feed things in slowly, keep the pieces small, and throw away anything that gives you pause—or makes a lot of noise.
With that said, the opposite is also true to some extent. A tablespoon of congealed bacon fat here or a handful of chopped celery there won’t instantly destroy your pipes or disposal, but over time, bad habits will come back to bite you in the ass. Treat your garbage disposal well—and clean it from time to time—and it’ll have your back for years to come.