3. Certain foods. Coffee grounds and eggshells shouldn’t go down your drain. Fibrous vegetables such as onions, celery and corn husks are also no-noes. Same with starchy foods: “Foods like potatoes, rice, and pasta can expand with water, creating a glue-like substance that clogs your pipes,” Shlomo Cherniak, owner of Cherniak Home Services, told Real Simple. Instead, put food waste in your compost bin.