hi, jy, I did not built it. I bought it a year ago.

not sure how it is grounded, it is clay based or sand based.

the floods start from last Dec, whenever it rains or snow melts, it is basically all over the floor of basement.

the photo is taken yesterday (the timestamp is wrong), it is near watermain, where every house here (the house is in Gatineau/Ottawa, Canada) has these drain caps. I just learned these things, all these caps were under a closet in basement, after I removed the floor carpet, floor plywood and found these things.

The house does not have sump pump, ground water supposed to be drained by weeping tiles (also called french drain) that connect to storm lines of the city.