In my basement there is a cap in the floor that is sealed with a wing nut. When it rains, it leaks and partially floods my basement. I have a couple questions. What is the purpose of the cap? Why does it flood? Is this cap something I can replace myself? Will replacing it solve my flooding problem? If it won't solve the problem, what can I do to stop the flooding? Sorry for the barrage of questions, but this keeps happening and I am now fully committed to fixing it. I greatly appreciate any help you could give me.