Question

why should we not throw cooking oil in the drain

Answer 1

Grease + Sewer = Fatberg. When you pour grease into your sink it's just beginning its travels. The grease and oil head down your pipes and into the sewers where they meet up with all the other wastewater from the area

Answer 2

After you’ve finished cooking some bacon or sautéing some vegetables, it’s easy to dump the excess grease and oil down the drain without giving it second thought. It’ll just get flushed away, right? Well, not exactly. Dump it in a cup, wait for it to cool, and throw it in the trash, because even a small amount of oil dumped down the drain can build up over the years and wreak havoc on not only your drainage system, but your town’s whole sewer.