The Five Worst Things to Put Down a Garbage Disposal, According to Plumbers

Garbage disposals are handy tools, allowing users to pulverize leftover food and send it through the drains, where it eventually lands in the sewer or septic tank. But as nifty as it is to rinse stuck-on food down the drain, garbage disposals can’t handle everything we throw at them.

We recently spoke to five experienced plumbers from across the country to get the low down on what’s safe and what’s not safe to put in a garbage disposal. All plumbers replied with similar answers, so if you’re sticking one of these five things down your disposal, stop immediately.

1. Eggshells

Contrary to popular belief, eggshells don’t sharpen garbage disposal blades. “Eggshells, often believed to be disposal-friendly, can surprise you by forming granules that stick to grease, compounding the clog issue,” says Al Fagundes, Master Plumber at A. Fagundes Plumbing and Heating.

Unless you’re interested in a slow buildup of eggshells that eventually cause a clog, start tossing those empty shells in the garbage or compost bin.

2. Starchy Foods

While most people know that flushing grease down the drain is a big no-no, not all realize the damage that starchy foods can do. According to Roy Barnes of Service Force Plumbing, the day after Thanksgiving is one of the busiest days for plumbers due to people clogging their drains with potato peels and starchy leftovers.

“Your garbage disposal will do a great job of grinding starches up into a sticky paste – the finer it grinds, the stickier the mess,” he says. To play it safe and prevent clogs, don’t put potatoes, potato peels, or pasta down your disposal.

3. Grease, Oil, or Animal Fats

All types of grease, including oil and animal fats (like bacon lard), can clog drains. Never place these in the garbage disposal or dump them down the drain. “Pouring grease down the drain may seem like a good idea when it’s a liquid, but as it cools, it will harden, causing clogging,” advises Chris Palmer of Raptor Rooter & Plumbing.

Even if the grease doesn’t cause an immediate clog, some of it will cling to the insides of the pipes, and then other bits of food will attach, slowly building up until the drains are impassable.

4. Fibrous Vegetables

Fibrous vegetables are great for the body but not so good for the garbage disposal. Jimmy Hiller of Happy Hiller, a multistate company that does plumbing and HVAC work, tells us, “Avoid fibrous or stringy foods such as celery, corn husks, onion skins, and artichokes. These can tangle the blades of the garbage disposal and cause it to jam.”

Toss your leftover veggies in the compost bin or trash to keep your blades sharp and jam-free.

5. Coffee Grounds 

One of the most controversial items you shouldn’t put down the drain is coffee grounds. Although some TikTokers claim that adding coffee grounds removes bad smells and sharpens garbage disposal blades, you can’t always believe what you see on social media. According to the master plumbers we’ve interviewed, this couldn’t be farther from the truth.

Dumping some coffee grounds may make your sink smell better, but it also creates a sludgy paste that sticks to the drains, eventually causing backups.

What Can You Put Down a Garbage Disposal?

Save your garbage disposal for the little bits of food that come off your plate as you rinse. Throw everything else in the trash or compost bin. Doing this will help prevent a costly (and inconvenient) plumbing emergency.