Plugging up infiltration point in basement floor

Hello, I'm having a flooding problem in which water is coming up into the basement through an opening in the slab where the bathroom drains come in. The foundation is otherwise bone dry.

I think what happens is that the city is doing something funny with the storm sewers under certain water conditions. Every once in a while, water builds up under the slab and bubbles in through this opening in the floor. First it bubbles, then it pours in. Typically the water reaches 2" deep across the whole basement floor and then starts to receed.

I am going to try putting a backflow preventor on the storm sewer connection on the chance that a backup in the sewer is flow back into my yard via the french drains.

NOW MY QUESTION -- I aslo need to plug up the hole in the slab and I am wondering the best way to do this. The drain pipes going down through the slab are PVC.

Thanks in advance.

hole

If the water is coming up through the slab, rather than out of a pipe, then sealing the hole will probably cause the entire concrete floor to raise and crack when the water backs up again.

foundation designed to be water proof

hcj said:

If the water is coming up through the slab, rather than out of a pipe, then sealing the hole will probably cause the entire concrete floor to raise and crack when the water backs up again.

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That's a good point, but the foundation was designed to resist water. I cannot describe the actual construction, except to say that it is designed like a bathtub with seals everywhere and there is tons of concrete and rebar in the slab. We also have gravel all around the house which should give the water somewhere else to go.