Recently, a damp spot has started to appear on the wall in the basement. At first, I thought it was just condensation, but the stain is growing, and now it smells musty. Maybe there is a leak in the drainage system or back pressure in the sewer? I don't know how to check without special equipment. Maybe someone has had a similar situation — where to start so that it doesn't turn into a flood? I also noticed that during heavy rain, this moisture increases, and there is a slight hissing sound near the wall, as if something is seeping under pressure. I'm very worried that the water will start to destroy the foundation or mold will appear, because we store things in the basement. Maybe it's worth digging a drain outside or checking the pipes with a camera, if possible? I want to avoid large expenses, but I also don't want to miss the moment.

Hello! The wall in my bathroom started to darken after my neighbors flooded it. At first, I thought they were just stains, but now they are growing. I guess it's mold? I don't know how to remove it properly so that it doesn't come back.