[Javs]

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.

[phishfood]

This is just a guess, but my thought is that the wing nut and cap seal a roof drain system cleanout. Do you you have a flat roof on you house that is drained by roof drains?

Otherwise, my second guess is that you have a septic system that is being flooded out by the rains, and the excess water is backing up through this sewer cleanout in your basement.

[havasu]

I'm wondering if this is suppose to contain one of those "one way" check valves, which we have spoken about previously, and needs replacing?

[Reedwalker]

Its a storm drain and its full of roots.

The wing nut is what we call around here an expansion plug. If I cut out a threaded cap and the threads get trashed in the process, this cap has a rubber gasket that expands when you tighten the wing nut.

Call a plumber!

[majakdragon]

Sounds like a Plumbers test plug to me. If you unscrew the wing nut, you can remove the plug. I would do that, when it is not raining, and see if the rubber seal on the plug is decayed or broken. You can buy new one.