What Do You Do When Someone Pours Oil Down the Sink?

To a person unaware of the potential damage, it might not seem like a big deal to pour liquid cooking oil down a sink. But that creates problems for home plumbing, sewers and the environment. Oil coats pipes, eventually causing clogs. Hardened cooking oil in sewer pipes can make sewage back up into the home, requiring expensive repairs. In community water systems, blockages from grease and oil can cause sewage backups into streets and waterways, creating public-health and environmental risks.

Dishes in sink with suds
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Remove cooking oil from cookware before washing it.

Uneffective Methods

When someone pours cooking oil down the drain, your first thought might be to help dissolve or break it down by using hot water, detergent, the garbage disposal or a drain cleaner. But these are not effective or, in the case of drain cleaners, should not be used regularly, according to the St. Vrain, Colorado, Sanitation District. Hot water cools down in pipes, causing oil -- and other fat and grease -- to harden farther down the sewer system. Detergents, even the ones that say they remove grease, also cause clogs further down in the pipe or system. Home garbage disposals are unable to remove grease and oils from plumbing. And drain cleaners, which can help break up oil-related clogs, are corrosive and, when used frequently, can damage the sewer line, requiring costly repairs.


A natural, noncorrosive remedy recommended by Michigan State University Extension is to pour 1/2 cup of baking soda down the drain, followed by 1/2 cup of white vinegar, which causes a lot of fizzing in the drain. Cover the drain to contain the fizzing action and, after five to 10 minutes, flush the drain with a kettle of boiling water. According to the extension, baking soda and vinegar can break down fatty acids into soap and glycerine and prevent clogs. A word of warning: To prevent burns and injury to the face or eyes, this method must not be used if a commercial drain opener has been used or is present in any standing water.

Best Method

The best way to dispose of home cooking oil is to pour it into containers with lids, such as empty glass jars. Allow the oil to cool and solidify, tighten the lid on the container and and deposit it in the trash. Or, save the oil in a resealable container and take it to a community cooking oil and grease drop-off location for recycling, if available in your area. Alternative fuels for diesel engines and home heating oil are made from recycled cooking oil, and it is an ingredient in some livestock feed, pet food and cosmetics. Additionally, it is best to wipe out cookware and any oily dishes or serving ware with an absorbent paper towel to remove oil before washing.

What Else Can't Go Down

Your local water and sewer agency can tell you what liquids can or can't go safely down your drain. The San Diego Metropolitan Wastewater Department, for example, has the typical requirements that liquids not be radioactive waste, hazardous chemical waste or untreated biohazardous waste; not be solids, sludges or viscous substances; and not have corrosive pH levels, grease or oil, and temperatures of 150 degrees Fahrenheit or higher in volumes of more than 10 gallons.