It's never a good idea to pour grease down a drain, even if you have a garbage disposal unit. The grease will inevitably cool and solidify before it is expelled from the home's plumbing system. Eventually, the solid grease will accumulate and block the drain or disposal unit altogether. The grease will also attract other debris that finds its way into the drain or disposal, contributing to a clog. Fortunately, it is possible to clear the grease from your drain and garbage disposal without having to call a plumber.
Remove any water that has backed up into the sink due to the clogged disposal unit. Use a cup or other small container to dip water from the sink and into a bucket.
Slice a lemon into sections that are small enough to fit down the drain. Turn on the garbage disposal and feed the lemon sections down the drain. As the disposal grinds up the lemon, the citric acid in the juice will help dissolve the grease that has accumulated within the unit and the drain.
Bring a large pot of water to a rapid boil. Pour the boiling water down the drain while the garbage disposal is running. The hot water will help melt away any remaining grease. If you notice that the boiling water is not draining as quickly as it should, move on to Step 4.
Pour 1/2 cup of baking soda into the drain, followed by 1/2 cup of white vinegar. Place the stopper in the drain or block the drain opening with a wet rag. Allow the baking soda and vinegar to remain in the drain for about 10 minutes. While you wait, boil another large pot of water. Add approximately 1 cup of salt to the boiling water.
Remover the stopper or wet rag from the drain and pour the boiling salt water down the drain and through the disposal. This will flush away the baking soda and vinegar, as well as any remaining grease.