What should I not put in the garbage disposal at the holidays?

Hot turkey drippings, bacon fat, and pan oil look harmless when they pour down warm and runny. The problem comes a few feet down the pipe. As the fats, oils, and grease cool, they harden and stick to the pipe walls. Each pour adds another layer, the pipe opening shrinks, and water backs up into your sink. This sticky group is common enough that the industry has a name for it: FOG.

The scale of the problem is not a guess. The U.S. EPA reports that grease is the single largest cause of reported sewer blockages, at 47 percent. That figure comes from the EPA's national report on sewer overflows, which found grease beat out tree roots and other debris as the top culprit. What clogs a city sewer main starts the same way in your kitchen pipe, just smaller.

Pouring grease down a drain with hot water and dish soap does not solve it either. The grease may move a little farther before it cools, but it still hardens somewhere in the line. Liquid cooking oil behaves the same way over time. The fix is simple: never put FOG in the disposal or any drain.

A disposal is built for small, soft food scraps rinsed off plates, not for clearing the whole holiday spread. Keep these out of it:

• Grease, fats, and cooking oils. They cool and harden in the pipe and build up clog after clog.
• Bones. Turkey, ham, and poultry bones are too hard for the grind system and can damage it or wedge in the drain.
• Fibrous and stringy vegetables. Celery, corn husks, asparagus, and artichokes have long strands that tangle around the grinding parts.
• Starchy foods. Potato peels, pasta, and rice swell with water and turn into a thick paste that coats the pipe.
• Coffee grounds and eggshells. They settle and pack together into a dense sludge at the bottom of the trap.
• Turkey skin and fat. This combines stringy texture with grease, so it both tangles and hardens.

When in doubt, throw the scrap in the trash instead of testing whether the disposal can handle it. A clogged line on a holiday weekend costs far more than a few seconds at the trash can.

Each banned food fails in its own way, and knowing why makes the rule easy to remember.

Bones are simply too hard. The grind system is made for soft food, and a bone can spin against the grinding plate without breaking down, which stresses the motor and leaves hard pieces to lodge in the drain.

Fibrous vegetables fail because of their long strands. Celery strings, corn husks, and artichoke leaves wrap around the moving parts like thread around a spool. They do not break apart cleanly, so they bind up the grinder and tangle in the trap below.

Starchy foods are sneaky. Potato peels, pasta, and rice may grind fine at first, but they keep absorbing water. They swell and turn into a gummy paste that clings to the inside of the pipe, narrowing it the same way grease does.

Coffee grounds and eggshells seem small and harmless, yet they do not dissolve. They settle out of the water and pack down into a gritty, cement-like layer in the trap. Over a holiday weekend of cooking, that adds up fast.

Using the disposal correctly matters as much as what you put in it. The manufacturer InSinkErator lays out a clear routine. Their guidance is to "run a steady stream of cold water" while you grind, and to keep it running for a few seconds after.

Here is the order that works:

1. 1Turn the cold water on first. A steady stream of cold water keeps any fats solid so they wash through instead of coating the pipe. Never use hot water, which melts grease and lets it cling downstream.
2. 2Turn the disposal on before adding food. Let it reach full speed, then start feeding scraps.
3. 3Feed it gradually. Add small amounts at a time rather than packing the chamber full. Small loads grind cleaner and drain better.
4. 4Keep the water running after. Let cold water flow for a few seconds past the last of the grinding noise to flush the bits all the way through the drain line.

Cold water before, during, and a few seconds after is the habit that prevents most holiday backups. If your disposal hums but does not spin, or the sink drains slowly even when the disposal sounds fine, those are separate problems worth checking.

Every banned item has a better home than the drain. Sorting scraps as you cook keeps both your disposal and the city sewer clear.

• Grease, fats, and oils should cool in an old can or jar, then go in the trash once solid. A simple grease jar by the stove catches drippings all season. Keeping FOG out of the system is exactly what municipal programs ask for: agencies like Portland's environmental services run public fats, oil, and grease programs because grease blockages cause sewer overflows that foul streets and waterways.
• Bones, fibrous vegetables, eggshells, and coffee grounds can go in the trash or, in many cases, a backyard compost pile. Vegetable trimmings, coffee grounds, and eggshells are all compost-friendly.
• Starchy scraps and turkey skin belong in the trash.

Keeping scraps out of the drain is not only about your own pipes. The EPA estimates there are tens of thousands of sanitary sewer overflows across the country every year, and blockages from grease and debris are a leading cause. Every jar of grease that goes to the trash instead of the sink is one less contribution to that problem.

A little sorting during holiday cooking saves you from a backed-up sink when the house is full of guests. Scrape plates into the trash, pour grease into a jar, and save the disposal for the small, soft bits it was built to handle. If a holiday clog does sneak through and the drain backs up, a plunger or a drain snake on the trap is the first move, not a chemical drain cleaner. Harsh chemical cleaners can sit in a blocked line and do more harm than good. For a line that stays slow after the meal is cleared, that points to buildup deeper in the pipe that needs a proper cleaning rather than another round of grinding.

A good habit for the whole holiday season is to keep a small trash bowl and a grease jar right on the counter while you cook. Scrape into the bowl first, rinse the plate second, and the disposal only ever sees the few soft bits that slip past. That one change prevents most of the clogs that fill a plumber's schedule the day after a feast.

For related drain questions, see our pages on why a garbage disposal is draining slow, what not to put down the drain in everyday use, and what to do when a garbage disposal is humming but not working. Together they cover the buildup, the bad habits, and the jams that turn a busy kitchen into a backed-up one.