Top 10+ Things That Should Never Go Down the Sink—But Often Do
Cooking Oil and Grease
Pouring cooking oil or grease down the sink might seem harmless, but it’s shockingly destructive. Once in the pipes, grease cools and solidifies, forming stubborn blockages called “fatbergs.” In 2024, the city of London removed a fatberg weighing over 40 tons from its sewers, a vivid reminder of the scale of the problem.
The U.S. Environmental Protection Agency has repeatedly warned that fats, oils, and grease are the leading cause of sewer overflows.
Even hot water and soap can’t prevent grease from clinging inside pipes. Instead, collect cooled oil in a jar and dispose of it in the trash.
Imagine your kitchen pipes slowly turning into a greasy, clogged artery—nobody wants that mess.
Coffee Grounds
Many people rinse coffee grounds down the sink without a second thought, but plumbers will tell you it’s a recipe for disaster. Coffee grounds don’t dissolve; instead, they clump together and stick to pipe walls, especially when mixed with grease or soap.
According to the Plumbing Manufacturers International, coffee grounds are among the top culprits for kitchen clogs. Clogged drains can lead to expensive repairs and even unpleasant backups.
Composting coffee grounds is a much smarter choice, not only for your plumbing but for your garden as well. Plus, think of all the money you’ll save on emergency plumber visits.
Eggshells
Eggshells seem innocent, but their sharp, gritty edges can create serious issues. When ground up in a garbage disposal, tiny shell fragments combine with grease and soap to form a thick paste that sticks to pipes.
Multiple city water authorities, including New York’s Department of Environmental Protection, have issued public warnings against sending eggshells down the drain. Pipes aren’t designed to handle this gritty sludge, which can harden and narrow the passage for water.
It’s better to toss eggshells in the compost or trash. Small habits like this keep your plumbing running smooth and hassle-free.
Medication
A surprising number of people flush expired pills or pour liquid medicines down the drain, not realizing the environmental consequences. According to the U.S.
Food and Drug Administration, traces of pharmaceuticals have been found in rivers, lakes, and even municipal drinking water across the country. These chemicals can disrupt aquatic life and enter the human water supply.
In 2025, the World Health Organization reported a growing concern about the presence of antibiotics and hormones in freshwater systems. Instead, use medicine take-back programs or return unwanted prescriptions to your pharmacy.
Every pill kept out of the water makes a difference.
Flour and Dough
Mixing flour with water makes glue, and that’s exactly what happens when flour goes down your sink. It quickly forms a sticky paste that coats pipes and traps other debris, leading to slow drains and eventually full blockages.
According to recent advice from the National Association of Clean Water Agencies, flour is a hidden hazard for home plumbing. Dough is even worse—it expands and hardens as it dries, creating stubborn clogs.
Scrape mixing bowls into the trash before washing. Remember, what seems soft and harmless in the kitchen can turn into a rock-solid nightmare in your pipes.
Paint and Solvents
Rinsing paintbrushes or dumping leftover paint down the sink sends toxic chemicals straight into the water system. The Environmental Protection Agency warns that paint contains heavy metals and volatile organic compounds, both harmful to aquatic life and human health.
Even “eco-friendly” paints can disrupt wastewater treatment processes. In 2024, several U.S.
states introduced stricter regulations on paint disposal, following new research linking solvent pollution to fish die-offs. Always check local hazardous waste guidelines for safe disposal.
Protecting water sources starts with small choices at home.
Wet Wipes and Paper Towels
It’s tempting to think that wet wipes labeled “flushable” or a single paper towel will break down in water, but research says otherwise. According to Consumer Reports in 2024, most wet wipes don’t disintegrate like toilet paper.
They tangle with other debris and create massive blockages in municipal sewers—sometimes called “ragbergs.” The problem has become so severe that cities like New York and Sydney spend millions annually clearing wipes from pipes. Toss wipes and paper towels in the trash instead.
It’s a simple step with a huge impact.
Food Scraps and Peels
Leftover vegetable peels, rice, and pasta often end up swirling down the drain, but these foods swell with water and create pipe obstructions. The Water Research Foundation found that starchy scraps are a leading cause of blockages in home plumbing.
Food waste in water systems also increases the load on wastewater treatment plants, making them less effective. Compost bins or green waste bins are a better destination for most scraps.
By keeping food out of the sink, you’re helping both your pipes and the planet.
Produce Stickers
Those tiny stickers on apples and avocados might seem harmless, but they cause outsized problems. Made from plastic or vinyl, produce stickers don’t dissolve in water.
Water authorities in Australia and Canada have reported that stickers frequently clog filters and pumps at water treatment plants. Even worse, they can slip past filtration and end up polluting rivers and oceans.
Always peel off and throw away stickers before washing produce. It’s a tiny habit that prevents big headaches downstream.
Cat Litter
Some brands of cat litter claim to be flushable, but wastewater experts strongly disagree. Cat litter doesn’t dissolve; it clumps and expands when wet.
In 2025, the American Public Works Association highlighted cat litter as a major cause of pipe blockages. More alarmingly, used litter can contain Toxoplasma gondii, a parasite that survives wastewater treatment and threatens wildlife, especially sea otters and other marine mammals.
Always bag and toss used litter in the trash. Even one scoop can make a big difference for local wildlife and your plumbing.
