Shower drain is not draining, bubbling + water is coming out of the drain

Hello dear community,

I have had a problem with my shower and the drain for 3 days. The water no longer drains. Connected to the shower drain are the bathroom sink, the toilet, and the kitchen sink in the kitchen next to the bathroom.

When I turn on the water at the kitchen sink, it bubbles in the shower and after a few seconds the water comes out of the drain. When I turn on the bathroom sink, it only bubbles. I have now bought a pressure air gun for drains because I assumed the drain was clogged, but even after using the gun several times, there is no improvement.

I then tried to unscrew the drain at the shower, which worked for a few turns. Then the screw in the drain would not move anymore. But after the screw was loosened a little bit, water suddenly started dripping from the ceiling one floor below.

I managed to tighten the screw again with effort and since then nothing has been dripping downstairs. Now my question is, what do I have to do now?

I hope you can help me

Hmm, a picture is worth a thousand words.

Is there a vent in the stack?

Purely based on the description, it sounds like a clog somewhere.

If it drips one floor below, then you should do nothing more, but get a professional. And do it quickly.