"Putting eggshells down your drain/garbage disposal. Tons of people do it. It can create a cement and clog your drain. A plumber told my wife that decades ago so we never did it. I figured there’s no harm in not doing it so better safe than sorry.

Then some friends of ours had plumbing problems. Lucky for them, the point of compaction was above an unfinished room so it was easy to get to. He cut out a section of PVC pipe and it was like a chunk of cement inside. All caused by eggshells."