One of the most efficient methods is to make a solution of baking soda, vinegar, and salt. The ratio is 1 cup of baking soda, ¾ cup of vinegar, and 1 cup of salt. Pour the mixture down the drain and follow with six cups of boiling water. This will create a fizzing mixture that should be poured down the drain, and in an hour or so, the starch should be dissolved.