Fat, oil and grease
An old timer in this list, fat, grease and oil, are tunneled into the sewage system by a lot of people, causing severe clogging in pipes. Although hot oil, or grease look like liquid, but they form a solid like slime when they cool down, causing a massive “stuck toilet” frenzy. Always try to reuse cooking oil. When you need to dispose, let them cool down and throw in the trash.