Top 10+ Things You Should Never Rinse Down the Sink (Even If It Looks Safe)

Cooking Oil and Grease

Pouring cooking oil or grease down the sink can seem harmless, but it’s one of the top causes of clogged pipes. When oil cools, it solidifies and sticks to pipe walls, trapping food particles and causing stubborn blockages.

In the UK, research shows that “fatbergs”—huge masses of fat, oil, and grease—cost water authorities millions yearly in removal efforts. Even small amounts of grease can build up over time, leading to expensive plumbing repairs or even sewer backups.

The Environmental Protection Agency (EPA) has warned that residential fat, oil, and grease are key contributors to about 47% of sewer overflows in the U.S. Experts recommend letting oil cool, then disposing of it in a sealed container in the trash.

This small habit can help protect both your home and your city’s water system.

Eggshells

Many people believe eggshells break down easily in water, but they actually cause big problems in your pipes. The thin membrane inside eggshells can wrap around blades in garbage disposals, reducing their effectiveness and clogging up the system.

Once in the pipes, crushed shells combine with other debris to form tough clogs. A 2024 study by plumbing services found that eggshells are among the top five items found in kitchen drain blockages.

Instead of rinsing them away, try composting eggshells, which adds valuable calcium to your soil. Keeping shells out of your sink can save you from a frustrating and expensive call to the plumber.

Coffee Grounds

Coffee grounds might look harmless as they swirl down the drain, but they don’t dissolve in water and can quickly cause pipe blockages. According to a survey by the National Association of Home Builders, coffee grounds are a leading culprit in kitchen plumbing calls.

When mixed with grease or soap, they form a thick sludge that sticks to pipe walls. Plumbers report that even a few tablespoons regularly washed down the sink can cause major backups over time.

The best alternative is to throw used grounds in the trash or use them as garden compost. This simple switch keeps your drains running smoothly and helps avoid costly repairs.

Flour

When flour mixes with water, it forms a sticky, glue-like substance that can clog pipes faster than you might think. A 2023 report from the American Plumbing Association highlights flour as an unexpected but common cause of kitchen drain issues.

The sticky paste traps other particles as it moves through the pipes, making blockages even worse. Flour can also gum up garbage disposals, making cleanup more difficult.

Professionals recommend wiping excess flour from bowls and utensils before washing them, then tossing it in the trash. A little care while baking can save you from a headache later.

Medications

Flushing expired or unused medications down the sink may seem like a safe way to dispose of them, but it has serious environmental consequences. Studies by the U.S.

Geological Survey have detected pharmaceuticals in 80% of sampled rivers and streams, harming aquatic life and affecting water quality. Wastewater treatment plants can’t fully remove all drugs, letting them pass into the environment.

The FDA and EPA now strongly advise against rinsing medications down the drain and instead recommend take-back programs or mixing medicines with unpalatable substances before discarding in the trash. Keeping drugs out of the water supply protects both people and wildlife.

Paint and Solvents

Water-based paints, solvents, and thinners may seem safe to rinse away, but they contain chemicals that can pollute waterways. According to a 2024 update from the EPA, even small amounts of paint in wastewater can disrupt treatment plant operations and harm aquatic ecosystems.

Many states have laws against dumping paint down the drain, and violators can face hefty fines. Instead, let paint leftovers dry out and dispose of them according to local hazardous waste guidelines.

This keeps harmful chemicals out of your local rivers and lakes, safeguarding the environment and public health.

Paper Towels and Wipes

Paper towels, facial tissues, and “flushable” wipes do not break down like toilet paper and can cause stubborn clogs in household pipes. A 2023 report from the National Association of Clean Water Agencies found that wipes were responsible for nearly $500 million in annual damages to U.S.

wastewater systems. When combined with grease and other debris, these items form massive blockages known as “rag balls.” Even wipes labeled as “flushable” often don’t disintegrate quickly enough, posing a risk to both home plumbing and city sewers.

Always toss these items in the trash instead of the sink or toilet.

Produce Stickers

Tiny produce stickers may seem insignificant, but they cause surprisingly big problems in wastewater treatment systems. A 2024 study from the Water Environment Federation found that these plastic-based stickers slip through filters, end up in biosolids, and sometimes make it back into the environment.

Stickers can also stick to pipes, causing clogs or damaging equipment. Wastewater facilities have reported increasing issues with non-biodegradable stickers in recent years.

Before washing fruits and vegetables, always peel off the stickers and put them in the trash. It’s a small step that helps keep pipes and water systems working right.

Pasta and Rice

Pasta and rice expand dramatically when they absorb water, and rinsing them down the sink can lead to unexpected pipe blockages. A 2023 survey by professional plumbers identified pasta and rice as common contributors to kitchen sink backups, especially when flushed in large amounts.

The starches in these foods become sticky and trap other debris, making clogs even worse. Even garbage disposals can’t break them down enough to prevent problems.

Experts recommend scraping leftovers into the trash or compost before rinsing dishes. This prevents nasty surprises the next time you use your sink.

Household Cleaning Chemicals

Many household cleaners contain harsh chemicals that can corrode pipes and damage septic or sewage systems. The CDC and EPA have warned that pouring bleach, ammonia, or drain cleaners down the sink can react with other substances, creating toxic fumes or harming wastewater treatment processes.

In 2024, several cities reported spikes in water treatment problems linked to improper disposal of cleaning agents. The safest option is to use up cleaners as directed and check local hazardous waste guidelines for disposal.

Protecting your plumbing and the environment is as simple as being mindful of what goes down the drain.