The essentials
- Garbage disposals use impellers, not blades, so there is nothing to sharpen, and eggshell membranes can lodge in the grinding chamber and cause blockages.
- Fats, oils and grease should never go down any drain; the EPA names grease from restaurants, homes and industrial sources the cause of 47 percent of reported sewer blockages.
- Run cold water before, during and for several seconds after grinding; cold keeps small amounts of grease solid so the unit can break them up.
- Large amounts of rice, pasta and potatoes turn to a mush that clogs the drain and P-trap, and fibrous scraps such as celery and corn husks wrap around grinding parts.
- Never reach into a jammed disposal by hand; unplug the unit, use long needle-nose pliers, and call a plumber if it hums, leaks or drains slowly.
A garbage disposal attracts more bad advice than almost any appliance in the house. Eggshells sharpen the blades, hot water flushes grease away, lemon peels clean everything: most of us have heard at least one of these, usually from a relative. Some of it is harmless, and some of it ends with a plumber snaking the drain line under the sink. Below, we sort the common beliefs from what disposal manufacturers and plumbing and wastewater professionals actually say.
Myth or Fact? Eggshells Sharpen the Blades
Myth, and the premise itself is wrong: a garbage disposal has no blades. The grinding chamber uses impellers, blunt metal lugs mounted on a spinning plate, something Consumer Reports confirmed with disposal manufacturers and wastewater treatment experts. There is nothing sharp in there to sharpen.
Eggshells still cause trouble, just not the way the myth claims. The thin membrane inside a shell can lodge around the grinding components and create a blockage. InSinkErator’s own guidance is more forgiving: the company says eggshells and coffee grounds pass through its disposals without harming the unit, but both are sedimentary, and feeding in too much at once, especially through older or neglected plumbing, can cause a clog or a slow drain. If you use the disposal for shells at all, feed them in gradually with a strong flow of cold water. The trash can or compost pile remains the safer destination.
Can You Really Put Grease Down the Disposal?
Myth, and it is the costliest one on this list. Bacon grease, cooking oil, pan drippings, butter, salad dressing and even creamy foods such as peanut butter, heavy cream and ice cream all fall into the category plumbers call FOG: fats, oils and grease. They may go down as a liquid, but they congeal as they cool, first inside your drain line and then inside the sewer main.
The scale of the problem is well documented. The EPA reports that grease from restaurants, homes and industrial sources is the most common cause of reported sewer blockages, accounting for 47 percent. A wastewater engineer in the Atlanta area puts grease’s role in sewer overflows at up to 65 percent. On the septic side, FOG solidifies in tanks and lines and can cause backups and expensive repairs.
Grinding does not solve it either. The Texas Commission on Environmental Quality makes the point plainly: grinding food waste does not remove FOG, it only breaks the greasy scraps into smaller pieces that still carry the fats into the pipes. The fix happens before the sink: pour cooled oil into a sealable container and put it in the trash, mix larger amounts into clay cat litter until absorbed, or check whether your city’s household hazardous waste collections accept used cooking oil.
Lemon Peels, Rice and Other Foods That Cause Trouble
Myth: the disposal is a second trash can. These units are designed for small, soft food scraps, and plumbing guidance is blunt about the rest. Starchy foods are a leading offender. Large quantities of rice, pasta and potatoes break down into a mush that can clog the drain and gum up the disposal, and cooked rice and pasta swell as they absorb water, packing tightly into the P-trap, the curved pipe under the sink that holds a seal of water. For more on that fitting, see our guide to how a P-trap keeps sewer gas out of your house.
Fibrous scraps are the other big group. Celery, corn husks, artichokes, asparagus, rhubarb and edamame pods carry long, stringy fibers that wrap around grinding components and stall the motor, often leaving the unit humming without grinding. Thin potato peels can slip through without being chopped first, and onion skins have a membrane that behaves much like an eggshell’s. Coffee grounds deserve a special mention: despite their reputation, they do not clean the disposal, and they sink, settle and gradually compact inside the drain line over time.
| Food scrap | Why the guidance says keep it out |
|---|---|
| Grease, oil, butter, dairy | Solidifies in pipes; the leading cause of sewer blockages |
| Rice, pasta, potatoes in quantity | Turn to a mush or paste that clogs the drain and P-trap |
| Celery, corn husks, asparagus, artichokes | Stringy fibers wrap around the grinding parts |
| Coffee grounds and eggshells | Sedimentary buildup, especially in older plumbing |
| Wipes of any kind | Break into small pieces that give grease something to cling to |
What about hard items? Here the sources genuinely split. Manufacturers say modern disposals handle fruit pits, small bones and cooked meat without breaking, because there are no blades to dull. Plumbers counter that small bones and pits, peach pits included, still get stuck and jam the unit. A practical middle ground: if you cannot chew it, treat it as too hard for your drain, and scrape bones and pits into the trash.
Does Hot Water Help or Hurt While Grinding?
Myth. Hot water feels like it should carry grease away, and that is exactly the problem. Hot water melts fat off your dishes and sends it down the pipe as a liquid, where it cools further along and coats the inside of the plumbing. The Texas Commission on Environmental Quality advises rinsing greasy dishes and pans with cold water before they go in the dishwasher for precisely this reason.
Cold water does the opposite of what people fear. It causes small amounts of grease to solidify, which lets the disposal break that grease into pieces that flush out instead of smearing down the pipe walls. That is why the manufacturer-recommended routine is cold water before, during and for several seconds after every run. Save the hot tap for washing up, not for the disposal.
Ice Cubes and Citrus: What Actually Cleans a Disposal
Myth, mostly. The ice-cube trick fails for the same reason the eggshell trick does: there are no blades in the chamber, so there is nothing to sharpen or resurface. Citrus peels get a more mixed verdict. A small piece of peel will not jam a modern unit, but fibrous peels sit in the same category plumbers flag for trouble, and a peel-based perfume does nothing about the grease film that actually causes odors.
What the sources support instead is unglamorous. Scrape plates into the trash before they reach the sink. Fit a catch basket or screen over the drain to trap small scraps while you rinse or trim food. Run cold water before, during and after grinding. Keep FOG out entirely, and keep coffee grounds out too, because grounds marketed as a scrub only settle and pack in the drain. Prevention, not grinding, is the cleaning method that holds up.
When the Jam Is a Job for a Plumber
Safety first
Never reach your fingers into a jammed disposal, even with the switch off. Dislodging a stuck object can release the mechanism and let the unit start unexpectedly. Unplug the unit or shut off its breaker, then use a tool such as long needle-nose pliers to pull out whatever is stuck.
A jam you can see and grip with a tool is often a do-it-yourself fix. The signs of a deeper problem are harder to miss: the unit hums without grinding, drains slowly, leaks into the cabinet, or clogs repeatedly. Those symptoms point to a blocked or failing unit, or a clog forming downstream in the drain line, and a plumber can clear the line and tell you honestly whether repair or replacement makes more sense.
The first garbage disposal was invented in 1927, and the units have been common in American kitchens for decades. The plumbing they connect to is often far less forgiving than the appliance itself, especially in houses with older or long-neglected drain lines, and that plumbing is usually where the real clog lives.
Related guides
- Getting started with replacing a kitchen faucet: the shut-off valves and supply lines you learn there are the same ones you will meet under the sink if you ever swap out a disposal.
- 8 ideas for a small bathroom update: low-cost, high-impact fixes for the other hard-working wet room in the house.
Common questions
Are eggshells bad for a garbage disposal?
The disposal itself usually passes them, but shells are sedimentary. Too many at once, or older plumbing that has not been cleared in some time, can create a clog or a slow drain.
What water temperature should I use with a garbage disposal?
Cold. Cold water keeps small amounts of grease solid so the disposal can grind them, while hot water melts grease that later cools and coats your pipes.
Can I put rice or pasta down the disposal?
Small dregs on a plate are one thing, but large quantities of starchy foods turn into a thick paste that can clog the drain and gum up the disposal. Toss big portions in the trash.
When should I call a plumber instead of fixing it myself?
If the disposal hums without grinding, drains slowly, leaks or clogs repeatedly, have it checked. Also call a professional if you cannot free a jam safely with a tool.
This guide is general information, not professional advice. Follow the manufacturer’s instructions and your local building codes, and hire a licensed professional for electrical, gas, structural or roofing work.