How do you remove black stains from floor grout?

soap.

Let it soak for 5 minutes, then scrub it well with a toothbrush and rinse it off.

White vinegar

White vinegar can be used in countless ways. In addition to thoroughly cleaning grout, it is also effective against limescale and mold.

Pour vinegar on the joints.

Add some baking powder.

Scrub thoroughly with a toothbrush and then rinse off.