Drill a hole in the base plate pressure-tight against groundwater, then concrete it

Hello,

I need your collective knowledge again. In my basement, the drainage from the roof passes through the floor slab into the sewer. A year ago, I replaced the 90-degree elbow because it was broken. Now, however, the groundwater is pushing into the basement between the old concrete and the new concrete.

How can I make the concrete joint to the old floor slab watertight against pressure water? I was already thinking of first filling 25% of the hole with quick-setting concrete, then pouring in bitumen and letting it harden, and then filling the rest with normal concrete.

Idea 2:
- Fill 25% with quick-setting concrete
- Coat / plaster the hole with sealing slurry
- Fill the rest with screed concrete

Are there better ideas or possibilities?
Thank you in advance for your help.

In case of pressing water, I would call in a specialist company. They seal the leaking spot with epoxy.

I would also rather hire a professional company, but if you definitely want to do it yourself: I would first apply sealing slurry. Otherwise, moisture could penetrate the floor slab through the quick-setting concrete. So first sealing slurry and mix it relatively thick. When it has cured, I would apply an acrylic joint around the pipe. I would fill the rest with [WU-Beton], although honestly, I don't know what it consists of. Will the room remain a usable basement? I would not lay tiles or similar over this construction.

A bathroom is actually supposed to go in that room. That's why it has to be completely sealed. Thanks for your info / tips so far.

Then I would definitely hire a professional company. If moisture still comes up in the end, the tiles will come loose. That would be saving in the wrong place.

Maybe can still contribute some expertise.?