A sink drain clogged by cooking oil is one of the most unpleasant misfortunes that can befall a harmonious household. Hideous smells, flooded floors and electricity outages are just some of the consequences of a blocked drain. Clogged sink drains can be particularly damaging to businesses such as restaurants, for which running water is a necessity. Fortunately, a drain blocked by oil usually can be prevented or cured without professional assistance.

...
A correctly flowing sink is handy for food preparation.

Prevention

Oils used in cooking, such as vegetable oil and olive oil, should not be disposed of down a sink drain or garbage disposal. Fats present in the oils harden when they contact cold water, especially when they were heated during cooking. The hardened fats create rigid deposits in drain pipe, leading to blockages. Drain the oil from a meaty stir-fry into a cup rather pouring it down a sink drain when you finish cooking. The fats will coagulate in a matter of hours, allowing the oil to be discarded in the garbage.

Plunger

Plungers are an old-fashioned way to tackle drain clogs such as oil, and they are still highly effective. A plunger works by creating a vacuum seal at the head of the plunger, which pulls trapped water and blockages toward the plunger head. Because fat oils solidify when they cool, a plunger can be used to remove them just as effectively as it removes other drain pipe debris.

Detergent

Oil deposits can be cleared from drain pipes by diluting their density. Mix a cupful of detergent with hot water, and pour the mixture down the clogged sink. The hot water should help soften the oil deposits as the detergent breaks them down. Running warm water from the sink's faucet for a couple of minutes after applying the detergent-hot water mixture flushes out the pipes thoroughly. Failing to flush the pipes with warm water may cause remaining oil deposits to re-harden.

Commercial Drain Cleaners

Chemical drain cleaners available from supermarkets and hardware stores include stringent chemicals that break down dense deposits such as cooking oils. Most of the drain cleaners take effect in 20 to 30 minutes, during which time their chemicals work on the deposits. Flushing the affected drain pipe with warm water after a chemical cleaner removes a clog prevents permanent damage to the pipe from the chemical cleaner. Wearing protective clothing such as gloves and goggles when using a chemical cleaner prevents it from causing burns and eye aggravation.