The best way to avoid grease clogs in drain pipes is to never pour grease or oil into a drain. Residual build up of grease and oils in sink drain pipes and the P-trap under the sink may be unavoidable, however. On occasion, someone might inadvertently dump grease or oil into a drain and cause a clog. If the clog is minor, some home-grown solutions may take care of the problem, and some simple maintenance can stop them from occurring in the first place.
Chemical and Enzymatic Cleaners
Chemical drain cleaners are designed to quickly remove clogs by chemically dissolving grease, oil and other solids. Some cleaners use chemicals such as sulfuric acid or sodium hydroxide to dissolve organic materials and grease in drains. These chemicals may be effective, but they're corrosive and may damage plumbing, so they shouldn't be used when a drain is entirely clogged because they will corrode plumbing as they sit in the drain. These chemicals can also produce toxic fumes when they're mixed with other household cleaners, so they must be used with caution.
Other commercial drain cleaners contain enzymes or bacteria that will naturally dissolve grease; these products tend to work more slowly than acid-based cleaners and may not be able to clear a tough grease clog. Enzymatic cleaners may be effective, however, at cleaning pipes after the clog has been cleared.
Water, Vinegar and Baking Soda
Vegetable oils are liquid at room temperature, and solid grease dissolves when it's heated, so an easy way to remove minor grease and oil deposits and keep your drains running smoothly is to run very hot water through your drains at least once a week.
If the drain is already running very slowly or is blocked entirely, you can add some common household ingredients to boost the water's cleaning power. Dump 1/2 cup of baking soda directly into the drain, and then pour in 1/2 cup of vinegar. Allow the baking soda and vinegar to sit in the drain for 10 to 15 minutes, and then flush the drain with hot water. Repeat the process to thoroughly clean the drain.
You don't want to use hot water to dissolve grease is when the grease or oil is in a kitchen sink equipped with a garbage disposal. Hot water will keep the grease in a liquid form and flush it through the garbage disposal and into the trap or drain pipe beyond.
If you inadvertently put grease or oil into the garbage disposal, run cold water into the garbage disposal to solidify as much grease as possible while it's still in the disposal. Run the disposal while you're running the cold water, and only run hot water through the disposal after it's clear of grease and oil.
Using a drain snake -- a metal cable that you insert through the drain pipe and twist to remove clogs -- can help you to dissolve grease that has entirely clogged the drain even if the snake itself does not entirely remove the build up. After the snake has punched a hole through the clog, run hot water through the drain; now that water can flow freely past the clog, the hot water may be able to dissolve the grease and flush the build-up away.
Call a Plumber
If none of these methods works, or if you're uncomfortable trying any of them yourself, consult a plumber or drain-cleaning technician. Sometimes clogs are deep in the drain, well beyond the trap, and home-made remedies may not be able to reach and effectively remove them. A professional technician will know which solutions are most effective, safe and appropriate for your situation.