By SemperScreen®. We own residential and commercial real estate properties across the United States, and we built the permanent sink screen for our own buildings before we sold it to anyone else.
What causes kitchen sinks to back up? Fats, oils, and grease are the foods to suspect most often when kitchen sink drains keep clogging. Grease cools, sticks to the pipe, and catches the food behind it.1 Other common culprits are fibrous vegetables, starchy foods, coffee grounds, and eggshells. Keep all 10 foods below out of the kitchen sink drain, with or without a disposal. Scrape them into the trash or compost and keep a screen in the drain for what slips past.2
What are the top 10 foods that cause clogged drains?
Grease leads the list. EPA's report to Congress on sewer overflows found that grease from restaurants, homes, and industrial sources caused 47 percent of reported blockages, more than any other cause.3 Here are the 10 foods we keep out of the drains in our own buildings, and why each one causes trouble.
1. Fats, oils, and grease (FOGs)
FOGs should never go down disposals or drains. They start as liquids, then congeal and coat the pipe, and that film catches other food and debris until water can't get through.1 Hot water and soap only carry grease farther down the line, where it cools and hardens.2
Fats, oils, and grease are the most problematic type of food waste because they clog and coat pipes.3
Why they're problematic:
- Start liquid, solidify in pipes
- Coat pipe interiors
- Collect other debris
- Create stubborn blockages
Common offenders:
- Bacon grease
- Butter
- Cooking oil
- Pan drippings
- Salad dressing
- Heavy cream
- Mayonnaise
2. Fibrous vegetables
Vegetables like celery, asparagus, corn husks, and onion skins have long, stringy fibers that wrap around a disposal's grinder and tangle in the drain.
Why they're problematic:
- Fibers tangle in the grinder
- Create jams and blockages
- Resist grinding
- Can stop disposal motor
Common offenders:
- Celery stalks
- Asparagus
- Corn husks
- Artichokes
- Onion skins
- Pumpkin fibers
- Rhubarb
- Carrot skins
3. Starchy foods
Starchy foods absorb water and keep swelling, even after cooking. In disposals and pipes, they turn into a thick paste that clogs drains.
Why they're problematic:
- Expand when wet
- Form thick paste
- Stick to pipes
- Create complete blockages
Common offenders:
- Pasta
- Rice
- Potatoes and potato skins
- Bread
- Oatmeal
- Flour-based items
- Stuffing
4. Coffee grounds
Coffee grounds clump together when wet and settle in the trap and pipe as a dense, sandy sludge.
Why they're problematic:
- Clump when wet
- Create sand-like sediment
- Build up over time
- Form stubborn clogs
5. Eggshells
The thin membrane inside an eggshell can wrap around a disposal's grinder, and ground shells turn into sand-like grit that collects in the trap.
Why they're problematic:
- Membrane tangles in the grinder
- Ground shells create sediment
- Build up in P-traps
- Combine with other debris
6. Bones
Bones are too hard to grind cleanly, and even small fragments can jam a disposal or lodge in the pipe.
Why they're problematic:
- Too hard to grind
- Can break disposal components
- Get stuck in pipes
- Increase clog risk in older pipes
Common offenders:
- Chicken bones
- Beef rib bones
- Pork chop bones
- Fish bones
7. Fruit pits and hard seeds
Pits from peaches, plums, avocados, and mangos are too hard to grind and can damage a disposal.
Why they're problematic:
- Extremely hard
- Can damage the grinder
- Jam disposal mechanism
- Lodge in pipes
8. Nuts
A disposal grinds nuts into a sticky paste, much like peanut butter, and that paste coats the pipe.
Why they're problematic:
- Grind into paste
- Create sticky mess
- Coat pipes
- Trap other debris
Common offenders:
- Peanuts
- Almonds
- Walnuts
- Any nut variety
9. Shellfish and hard shells
Lobster, clam, oyster, and mussel shells are too hard to grind and break into sharp fragments that snag other debris.
Why they're problematic:
- Too hard to grind
- Can damage the grinder
- Create sharp fragments
- Clog pipes
10. Produce stickers
The little PLU stickers on fruits and vegetables stay intact in water, stick to the pipe wall, and collect debris. Peel them off before you rinse produce.
Why they're problematic:
- Don't break down
- Attract other materials
- Stick to pipes
- Eventually cause clogs
Where should each food go instead of the drain?
Use this as a sink-side checklist for your household or your units. Composting ranks above the trash on EPA's Wasted Food Scale, which places sending wasted food down the drain in its least-preferred tier.4 Where composting isn't available, the trash still keeps food out of your pipes. Our guide to starting a compost routine covers the setup.
| Food | Where it goes instead |
|---|---|
| Fats, oils, and grease | Cooled, in a jar or can with a lid, then the trash1 |
| Fibrous vegetables | Trash1 or compost |
| Starchy foods | Trash1 or compost |
| Coffee grounds | Trash or compost, never the drain or toilet1 |
| Eggshells | Trash or compost, never the drain or toilet1 |
| Bones | Trash |
| Fruit pits and hard seeds | Trash |
| Nuts | Trash |
| Shellfish and hard shells | Trash |
| Produce stickers | Trash, peeled off before rinsing |
Can food go down the drain if you have a garbage disposal?
A garbage disposal makes food smaller. Every ground-up piece still travels into the same pipe, and grease still coats the walls on the way. Sewer agencies tell kitchens to skip it. The Los Angeles County Sanitation Districts' kitchen poster lists best practices and recommends to avoid putting greasy foods down the drain using the garbage disposal and recommends greasy foods go to the trash.5
In a 2015 FAQ, the Tahoe City Public Utility District in California says two-thirds of sewer backups happen in the homeowner's own sewer line, and that they are frequently caused by things flushed down the toilet or ground up in the garbage disposal.2 A New Jersey county health department tells residents to use the disposal sparingly and to put any waste that can go in the garbage into the trash.1
If you're ready to take the disposal out, see what to install after removing a garbage disposal. SemperScreen® recommends that you always refer to local building codes when modifying a building's plumbing system.
Why do kitchen drains clog after Thanksgiving?
Roto-Rooter reports a 50 percent spike in service calls on the day after Thanksgiving and calls it the busiest day of the year for the plumbing industry.6 Holiday cooking sends 4 foods from this list toward the sink in one afternoon: pan drippings, potato skins, stuffing, and bread.
Set up before the guests arrive. Put a can by the stove for grease and a trash or compost bin next to the sink for plate scrapings, then make sure every kitchen drain has a screen in it.2
How do you keep these foods out of the drain?
These 3 habits cover the whole list:
- Can the grease. Pour cooled fats and oils into a jar or can with a lid, then put it in the trash.1
- Scrape before you rinse. Scrape plates, pots, and pans into the trash or compost before they go in the sink.1
- Screen every kitchen drain. Keep a screen in each kitchen sink drain and empty what it catches into the trash.2
For more ways to keep food out of the drain, see 7 ways to stop food going down the sink drain.
Why do the same kitchen drains keep clogging in rental properties?
We own rental buildings, so we pay for these clogs too. We learned this in a 33-unit, 1960s slab-on-grade apartment building in Los Angeles (the full story is on our About page).
Drain and plumbing clogs are one of the top three maintenance ticket categories, at $250+ per call. They come from human error that no training program fixes, and each turnover brings in someone who missed the last move-in talk about grease.
NIOSH, the federal workplace-safety research agency, rates engineering controls as more effective than administrative controls such as training, because engineering controls work without significant human interaction.7 A screen fixed in the drain works that way. A lease clause depends on whoever lives there this year.
"I am very excited about this. I am very impressed with the 12 I installed in 2022. Not only do I want to install in the rest of my properties but I also want to offer the product to my maintenance customers. Clogged kitchen sinks are such a constant in the rental industry"
Jason C, Home Run Maintenance and Properties
If you manage rentals and the disposal question has come up, read can a landlord remove a garbage disposal from a rental.
What does a permanent sink screen catch, and what does it miss?
The SemperScreen® permanent sink screen is the only non-removable permanent sink screen. It fits standard 3½" drains and stops food waste down to grains of rice, with a screen aperture of 0.08 in (2.0 mm). Cleaning is one step. Just scoop it out!
Liquids pass through any screen, including grease on its way to cooling in the pipe. The grease can stays by the stove no matter what's in your drain.
Our permanent sink screen is polished stainless (304 stainless steel). It installs in ~15 minutes per drain, retrofit, no plumbing modifications, and it was tested and COMPLIED with ASME A112.18.2-2020 / CSA B125.2-20. The test reports are on our site.
"Clogged drain lines in our apartment buildings are significantly reduced after installing SemperScreen® sink strainers. This product pays for itself 5 times over with just the first blockage or repair it prevents. Very few products in the apartment industry have that kind of return."
Patrick and Robert, BLVD Capital
For rental and property teams: We know you have at least one drain that keeps clogging (we have experience with those). Contact us and let's discuss testing our permanent sink screens in those bad drains.
Commercial properties (restaurants, hotels, retail breakrooms, hospitals, senior care facilities, office breakrooms, industrial warehouses) have some of the same issues with food waste, find out what we recommend in these larger facilities.
Frequently asked questions
What food causes the most clogging of pipes?
Fats, oils, and grease. They cool, stick to pipe walls, and trap the food that follows, which is why EPA's report to Congress found grease was the most common cause of reported sewer blockages.3
Can small bits of food go down the drain?
Keep them out when you can. Even a small amount of grease leaves a sticky film in the pipe, and small food bits build up on it until water can't get through.1 Scrape plates into the trash first, and let a screen in the drain catch the rest.2
Is it better to throw food away or use a garbage disposal?
Composting beats both. EPA's Wasted Food Scale places sending wasted food down the drain in its least-preferred tier, alongside landfilling and incineration, and ranks composting higher.4 If you can't compost, the trash still keeps food out of your pipes.
Can you put coffee grounds or eggshells down the drain?
No. A New Jersey county health department tells residents never to put coffee grounds or eggshells down the drain or the toilet.1 Grounds clump into sludge, and crushed shells settle as grit in the trap. Both belong in the trash or compost.
How do property managers keep tenants from clogging kitchen drains?
Lease rules and move-in reminders help until the next turnover. What lasts is a physical control: a screen fixed in each kitchen drain that residents can't remove, so food stays in the sink where it can be scooped into the trash.
References
- Montgomery Health Department, also serving the boroughs of Hopewell, Pennington, and Rocky Hill, New Jersey. "Your Drain Is Not A Trash Can! Think at the Sink!" Fats, oils, and grease brochure, undated. Hosted by the Borough of Pennington. Retrieved from https://www.penningtonboro.org/DocumentCenter/View/288/Your-Drain-Is-Not-A-Trash-Can-PDF
- Tahoe City Public Utility District. "What Not To Put Down Your Toilet or Drains: Frequently Asked Questions." February 19, 2015. Retrieved from https://www.tcpud.org/sites/default/files/documents/ffres.pdf
- U.S. Environmental Protection Agency, Office of Water. "National Pretreatment Program (40 CFR 403): Controlling Fats, Oils, and Grease Discharges from Food Service Establishments." EPA-833-F-12-003. September 2012. Retrieved from https://www.epa.gov/system/files/documents/2021-07/pretreatment_foodservice_fs.pdf
- U.S. Environmental Protection Agency. "Wasted Food Scale." Sustainable Management of Food. Updated September 9, 2026. Retrieved from https://www.epa.gov/sustainable-management-food/wasted-food-scale
- Los Angeles County Sanitation Districts. "Good Cleaning Practices: Managing Fats, Oil & Grease." Kitchen poster. Hosted by the City of West Hollywood. Retrieved from https://www.weho.org/home/showpublisheddocument/62584/638900756478970000
- Roto-Rooter. "'Brown Friday' After Thanksgiving: The Busiest Day of the Year for Plumbers." Press release, PR Newswire. November 20, 2025. Retrieved from https://www.prnewswire.com/news-releases/brown-friday-after-thanksgiving-the-busiest-day-of-the-year-for-plumbers-302622030.html
- National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. "Hierarchy of Controls." Updated April 10, 2024. Retrieved from https://www.cdc.gov/niosh/hierarchy-of-controls/about/index.html
